Print Bundle: PE Mechanical Machine Design & Materials
Make sure you have everything you need for PE Mechanical exam day success! This comprehensive collection of resources provides everything you need to pass the PE Mechanical Machine Design and Materials exam the first time. The review materials in this bundle are updated to the current exam specs, contain thorough coverage of mechanical engineering principles and codes, and include numerous practice problems to challenge your knowledge of those concepts. This curated bundle includes Michael R. Lindeburg, PE's Mechanical Engineering Reference Manual, the #1 reference manual in the industry, practice problems, and the most realistic practice exams on the market available in print or digital formats. PPI’s time-tested, detailed instructional design provides you with the most efficient and effective practice available.
Products Included:
- Mechanical Engineering Reference Manual
- Mechanical Engineering Practice Problems
- Mechanical Engineering Machine Design and Materials Practice Exam
- Mechanical Engineering Machine Design and Materials Practice Exam Updates and Corrections
- Engineering Unit Conversions
- Casio FX-115 ES Plus Second Edition Advanced Scientific Calculator
- Customizable Book Tabs
Topics Covered Include:
- Basic Engineering Practice
- Engineering Science and Mechanics
- Material Properties
- Strength of Materials
- Machine Design
- Vibration
- Mechanical Components
- Joints and Fasteners
- Supportive Knowledge
PPI bundle prices include 15% off individual product prices and free shipping!
$495.00
FAQs
It is an 8-hour exam. It contains 80 total questions: 40 multiple-choice questions in the 4-hour AM session, and 40 multiple-choice questions in the 4-hour PM session.
The PE structural exam is the only open-book exam remaining. All other PE exams are now closed-book computer-based exams, commonly referred to as CBT.
The PE exam can be difficult. The exam tests your competency in all aspects of engineering and should not be taken lightly. You should plan on taking several weeks to prepare and study before sitting for the exam. To see the average pass rate of first time test takers during the last exam, click here.
The PE exam tests for a minimum level of competency in engineering. You need a minimum of four years of post-college work experience to be able to sit for the exam.
What Our Customers Say
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."
Matthew
“Just wanted to let you know, I received results for PE Exam today…PASS!! Thank you to PPI…Specifically Josh Ogle and Richard Austin, my instructors for the April 2021 review courses."
Calvin
"The PPI surveying course was a good overview and provided many useful study materials. This course is particularly useful when paired with the PPI Civil PE Review Course since it amplifies some lessons you will have in the overall review session."
Keivan
"The study materials are very useful. The key to passing the exam is to practice as much as you can."
Nicholas
"All you need to do to pass this exam is work all of the homework problems assigned, work both of the practice exams, and go to class. Also, ask questions! The instructors are more than happy to answer them for you. That's about it!"
Jesse
"The course was great. Really helped with knowing just what kind of questions would be expected on the exam, and the review material was a great reference to bring to the exam!"
Tamara
"There is no better way to get to know the contents of MERM than the PPI Review Course. Highly recommended as a foundation for PE preparation."
PE Mechanical Customer
"This course is a must for everyone. It is much more difficult than the actual test, but it will leave no stone unturned. You WILL be prepared for the exam if you attend the lectures and do the homework."
Kevin
"The structure provided by the course is what I needed to force myself to sit down and study. The knowledge and test-taking tips from the instructor were very helpful. Course notes were a great reference on the exam. Quite often, class examples were very representative of actual exam problems."
Brad
"This was a good class overall. The best part was receiving a good study structure, being held accountable for doing it, and having a place to ask questions and review the concepts. I know this review course was the reason I passed. You also have to put in the effort, but it is worth it in the end."
Thomas
"This test is definitely not one to attempt without some help or guidance. PPI does a solid job of keeping attendees on a schedule and giving them an overall review of the required materials."
Ion
"This course is a good review prior to taking the PE exam. The instructor offered valuable advice that only experience could bring. Thank you for your guidance and thank you PPI. I highly recommend this course to everybody who wants to pursue a technical career."
PE Mechanical Customer
“The instructor was very knowledgeable in the exam topic areas and answered all questions. The course materials were very helpful in learning what will be on the exam. It was often more difficult than the actual exam questions, but they will prepare you for the test."
Justin
"This review course is very rigorous, but the amount of problems and difficulty of subjects cover what you need to be prepared for the exam. The course also allows you to interact with other PE exam takers to be able to ask them questions and learn from other students.”
PE Mechanical Customer
“The instructor provided basic theory and techniques that were very helpful in the homework, practice exams, and, of course, the actual exam. There was also good feedback and help from the other students. It's definitely hard work, but definitely worth it!"
Maureen
"I was very rusty in all of the areas I hadn't used in my day-to-day work. I have been out of school for 30 years, and the structured lectures and homework helped me get back in practice. I went into the exam nervous and left confident. I wouldn't have been able to do this without PPI."
David
"The course i s tailored to provide a structured roadmap to help you review all the required materials to master the PE exam. The instructor in particular was very helpful, and his tips were solid gold. I would definitely recommend the PPI course for future PE exam applicants."
Kelly
"This course is a great resource for studying for the PE exam. The course follows a rigorous but helpful schedule. The office hours are a great resource for anyone who needs questions answered outside of class. I felt very prepared going into the exam."
PE Mechanical Customer
“The interaction with the instructor and other students was very helpful and gave some great insights for preparation as well as content and problem solving methods. You will not regret taking this prep course because it will make you feel absolutely ready when you enter those doors on exam day."
Michael
"This course is a very valuable tool to prepare for the exam. Not only does it give a structured study plan to follow, but the instructor follows the topic breakdown, which ensures you keep up on your end as well. The class material, homework, and discussions were all great for preparation.”
Jesse
"This review course is well worth the time. The review materials are a good representation of what you could see on the PE exam. The live instructor feedback is valuable."