$P _{1} V _{1}= P _{2} V _{2}$
Since $V_{2}=2 V_{1}$ Hence $P_{2}=P_{1} / 2$ (isothermal expansion)
$P _{2}=1 \times 10^{7} Pa$
$P _{2}\left( V _{2}\right)^{\gamma}= P _{3}\left(2 V _{2}\right)^{\gamma}$
$P _{3}=\frac{1 \times 10^{7}}{2^{1.5}}=3.536 \times 10^{6}$
$A \rightarrow B :$ 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

