A force acting on a body moving along the x-axis is given by
$F(x)=\begin{cases}
a x, & 0\le x \le 2\,\text{m}
a(4 - x), & 2< x \le 4\,\text{m}
\end{cases}$
where a is a positive constant. Find the total work done by the force when the body travels from x=0 to x=4m.
a) 8aJ
b) 4aJ
c) 2aJ
d) 0J