A cylindrical adiabatic container of total volume $2{\mathrm{V}}_0$ is divided into two equal parts by a conducting piston which is free to move as shown in the figure. Each part contains identical gas at pressure ${\mathrm{P}}_0$. Initially the temperatures of the left and right parts are $4{\mathrm{T}}_0$ and ${\mathrm{T}}_0$ respectively. An external force is applied on the piston of area $\mathrm{A}$ to keep the piston at rest. The value of external force required when thermal equilibrium is reached is