Thermo Question

Water initially at $200$ kPa and $300C$ is contained in a piston$-$cylinder device fitted with stops. The water is allowed to cool at constant pressure until is exists as a saturated vapour and the piston rests on the stops. Then the water continues to cool until the pressure is $100$ kPa $.$ On the T$-$v diagrams sketch, with respect to the saturation lines, the process curves passing through both initial, intermediate, and final states on the process curves. Find the overall change in internal energy between the initial and final states per unit mass of water.

$(20$ marks$)$