2019:
In a cyclic process, the net heat absorbed or rejected is zero. Therefore, the work done is also zero.
2018:
In an isothermal process, the work done is given by $\text{W} = \int_{V_1}^{V_2} p\ dV = \int_{V_1}^{V_2} \frac{nRT}{V} dV = nRT \ln \left( \frac{V_2}{V_1} \right)$. Since $V_1 = V_2$, the work done is zero.
2017:
The work done in a cyclic process is given by $\text{W} = \oint p\ dV$. The area enclosed by the curve is $\frac{\pi}{2}\ R\ T$. Therefore, the work done is $\frac{\pi}{2}\ R\ T$.
