A frictionless piston-cylinder connected to a linear spring is filled with saturated liquid ammonia at some temperature (Tsat, Psat). When the piston touches the bottom of the cylinder, the spring is slightly compressed. The spring constant is K, and the cylinder has a uniform cross section A. The system is heated constantly by an external heat source, expanding the ammonia through vaporization, and pushing the piston at a constant speed of . For the beginning of the process, express the followings in terms of given parameters