One mole of ideal monoatomic gas at initial state a with pressure $P_0$  and volume  $V_0$ is taken to a final state $\text{'}d\text{'}$  with pressure $e^3{P}_0$  and volume $\frac{V_0}{e}$  through the path  $a\to b\to c\to d$ (figure)  $a\to b$ and  $c\to d$ are adiabatic paths where as $b\to c$  is isothermal with temperature  $T_0.$ Find the work done by the gas in the process $b\to c.$   (Given $ln\left(e\right)=1$ )