Plastic Deformation: Calculating Total Work Done

[look416]

Homework Statement

the graph below shows the behaviour of a sample of a metal when it is stretched until it starts to undergo plastic deformation.

what is the total work done in stretching the sample from zero extension to 12.0mm?
simplify calculation by treating the region xy as a straight line

Homework Equations

The Attempt at a Solution

i have used the formula total work done = area under the graph f-e
550x12x10^-3x0.5=3.3
which I am wrong.
wouldnt figure out the problem
the ans is 3.55J

 

[Mapes]

The problem says to assume x-y is a straight line, not to assume O-y (where O is the origin) is a straight line. Know what I mean?

 

[look416]

so the area x-y is a trapezium?
using rule of trapezium
0.5x(500+550)x2.0x10^-3
=1.05
plus the area before deformation
500x10x10^-3x0.5=2.5
2.5+1.05=3.55
yeah i got the answer thx