A piston-cylinder assembly initially contains water at a pressure of 300 kPa and a temperature of 250C. The water in the container becomes saturated steam at constant pressure and is left to cool until the piston stops. The curve of the process in the T-V diagram drawn by considering the saturation lines, for the water cooled down to a pressure of 100 kPa afterwards; the initial mood, the progress time and the final state are passed. Determine the final values of T, P, and V. Find the average internal energy change in the initial and final state, per unit water mass.