A piston of mass is hung from a massless spring whose restoring force law goes as , where k is the spring constant of appropriate dimension. The piston separates the vertical chamber into two parts, where the bottom part is filled with ' ' moles of an ideal gas. An external work is done on the gas isothermally (at a constant temperature T ) with the help of a heating filament (with negligible volume) mounted in lower part of the chamber, so that the piston goes up from a height to , the total energy delivered by the filament is: (Assume spring to be in its natural length before heating)