A cylindrical adiabatic container of total volume `2V_(0)` divided into two equal parts by a conducting piston which is free to move as shown in figure. Each part containing identical gas at pressure `P_(0)`. Initially temperature of left and right part is `4T_(0) and T_(0)` respectively. An external force is applied on the piston of area 'A' to keep the piston at rest. The value of external force required when thermal equilibrium is reached is.