A cylinder contains a piston on each side of which is one kilomole of an ideal gas. The walls of the cylinder are diathermal and the system is in contact with a heat reservoir at a temp of 273.15 Kelvin. The initial volume of the gaseous sub-systems on either side of the piston are 12 and 2 liters respectively. The piston is now moved reversibly so that the final volumes are each 7 liters. What is the change in the Helmholtz potential? (Note that this is the work delivered to the system by the reservoir)