State   1             ⇆     State   2    …

$$\begin{gathered} \mathrm{State} 1 \leftrightarrows \mathrm{State} 2 \leftrightarrows \mathrm{State} 3 \\ \left(\begin{array}{c}\mathrm{T}=300\mathrm{K}\\ \mathrm{P}=15\mathrm{bar}\\ 1\mathrm{mole} \end{array}\right)\left(\begin{array}{c}\mathrm{T}=300\mathrm{K}\\ \mathrm{P}=10\mathrm{bar}\\ 1\mathrm{mole} \end{array}\right) \left(\begin{array}{c}\mathrm{T}=300\mathrm{K}\\ \mathrm{P}=5\mathrm{bar}\\ 1 \mathrm{mole} \end{array}\right) \end{gathered}$$

The forward direction is expansion process and reverse direction is compression process. Overall process is isothermal process.

The net work done$={\mathrm{W}}_1+{\mathrm{W}}_2+{\mathrm{W}}_3+{\mathrm{W}}_4$

${\mathrm{W}}_1 \& {\mathrm{W}}_2$ are exapansion work

${\mathrm{W}}_3 \& {\mathrm{W}}_4$ are compression work

${\mathrm{W}}_1=-10\left(\frac{300\mathrm{R}}{15}-\frac{300\mathrm{R}}{10}\right)$

${\mathrm{W}}_2=-5\left(\frac{300\mathrm{R}}{10}-\frac{300\mathrm{R}}{5}\right)$

${\mathrm{W}}_3=-15\left(\frac{300\mathrm{R}}{5}-\frac{300\mathrm{R}}{10}\right)$

${\mathrm{W}}_4=-15\left(\frac{300\mathrm{R}}{10}-\frac{300\mathrm{R}}{15}\right)$

The net work done$=200\mathrm{R}=\frac{50}{3}\mathrm{L} \mathrm{bar}$