A poly-atomic molecule ( $C_{V}=3 R, C_{P}=4 R$, where $R$ is gas constant) goes from phase space point $\mathrm{A}\left(\mathrm{P}_{\mathrm{A}}=10^{5} \mathrm{~Pa}, \mathrm{~V}_{\mathrm{A}}=4 \times 10^{-6} \mathrm{~m}^{3}\right)$ to point $\mathrm{B}\left(\mathrm{P}_{\mathrm{B}}=5 \times 10^{4} \mathrm{~Pa}, \mathrm{~V}_{\mathrm{B}}=6 \times 10^{-6} \mathrm{~m}^{3}\right)$ to point $\mathrm{C}\left(\mathrm{P}_{\mathrm{C}}=10^{4} \mathrm{~Pa}, \mathrm{~V}_{\mathrm{C}}=8 \times 10^{-6} \mathrm{~m}^{3}\right) . \mathrm{A}$ to B is an adiabatic path and B to C is an isothermal path. The net heat absorbed per unit mole by the system is :[