An ideal gas ($1$ mole, monatomic) is in the initial state $\mathrm{P}$ (see diagram) on an isothermal curve $\mathrm{A}$ at a temperature $T_0$. It is brought under a constant volume $\left(2V_0\right)$ process to $\mathrm{Q}$ which lies on an adiabatic curve $\mathrm{B}$ intersecting the isothermal curve $\mathrm{A}$ at $\left(P_0, V_0, T_0\right)$. The change in the internal energy of the gas (in terms of $T_0$) during the process is  $\left(2^{\raisebox{1ex}{$2$}\!\left/ \!\raisebox{-1ex}{$3$}\right.}=\text{1.587}\right)$