A vertical piston-cylinder device, which is insulated, initially contains 15 kg of water, 9 kg of which is in the vapor phase. The pressure inside the cylinder is maintained constant at 0.3 MPa by mass of the piston. Now steam at 0.8 MPa and 500 °C is allowed to enter the cylinder from a supply line until all the liquid in the cylinder has vaporized. Determine (a) the final temperature in the cylinder and (b) the mass of the steam that has entered.