Stress-strain graph-finding elastic strain energy

[Krashy]

Homework Statement

Homework Equations

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stress = force/area
strain = extension/original length
Young modulus= stress/strain

The Attempt at a Solution

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Hi i hope you can read my handwriting. I solved task a already but even though i think i solved b correctly, the solution says its wrong. It states that its 45000 J. It could be a mistake in the book because its just off by one zero, but I am not sure it could be a mistake in my calculation too. The force and the extension is apparently right according to the solution.
Thank you very much in advance.

 

[mjc123]

I agree with your answer. Such mistakes in books are not uncommon, unfortunately.

 

[Krashy]

All right, thanks good to know i didnt miscalculated