A vertical cylinder of cross-sectional area `0.1m^(2)` closed at both ends is fitted with a frictionless piston of mass M dividing the cylinder into two parts. Each part contains one mole of an ideal gas in equilibrium at `300K`. The volume of the upper part is `0.1m^(3)` and that of lower part is `0.05m^(3)` .What force must be applied to the piston so that the volumes of the two parts remain unchanged when the temperature is increased to `500K`?