Arrange the four graphs in descending order of total work done;...

As seen from figure, work done in first graph, ${W}_{a} = 0$.

Now, work done in figure $b$, ${W}_{b} = + ve$, and that in figure $c$, ${W}_{c} = + ve$, $> {W}_{b}$.

In last graph, work done is ${W}_{d} = - ve$.

So, the descending order of total work done is

$⇒ {W}_{c} > {W}_{b} > {W}_{a} > {W}_{d}$

$⇒ {W}_{3} > {W}_{2} > {W}_{1} > {W}_{4}$