
$w _{\text {lat }}=200 \ J $
$Q _{\text {lat }}=500 \ J So U _{\text {lat }}=300 \ J$
So : $U_t=400 \ J$
$U_b=100 \ J $
$Q_b=100+50=150 \ J $
$Q_{b t}=300+150=450 \ J$
So the required ratio $\frac{Q_{b f}}{Q_{i b}}=\frac{450-150}{150}=2$
$A \rightarrow B :$ Isothermal expansion at temperature $T$ so that the volume is doubled from $V _{1}$ to $V _{2}=2 V _{1}$ and pressure changes from $P _{1}$ to $P _{2}$
$B \rightarrow C :$ Isobaric compression at pressure $P _{2}$ to initial volume $V _{1}$
$C \rightarrow A$ : Isochoric change leading to change of pressure from $P _{2}$ to $P _{1}$
Total workdone in the complete cycle $ABCA$ is
