Answer
$$\approx 39.1J $$
Work Step by Step
Graph is nearly triangle (if not perfect triangle)
So the area under curve is work done
$$W=\dfrac {F\times x}{2}=\dfrac {6800N\times 11.5mm}{2}=\dfrac {6800\times 11.5\times 10^{-3}}{2}\approx 39.1J $$
