Question

$w_{AB} = - nRT.\ln\frac{P_{1}}{P_{2}} = - 2 \times R \times 300 \times \ln\frac{1}{2} = + 600R.\ln 2$

$w_{BC} = - nRT.\left( T_{2} - T_{1} \right) = - 2 \times R \times (400 - 300) = - 200R $$${w_{CD} = - nRT\ln\frac{P_{1}}{P_{2}} = - 2 \times R \times 400 \times \ln\frac{2}{1} = - 800R.\ln 2 }{w_{DA} = - nR\left( T_{2} - T_{1} \right) = - 2 \times R \times (300 - 400) = + 200R }{\therefore w_{net} = w_{AB} + w_{BC} + w_{CD} + w_{DA} = - 200R.\ln 2 = - 100R.\ln 4}$$