A closed feedwater heater for a steam power plant operates as shown in the figure below. High-pressure liquid water at 10 MPa and 300C enters a series of heating tubes. Steam at 1.5 MPa and 95% quality is sprayed over the tubes and allowed to condensate. The saturated liquid is subsequently allowed to leave the device at station 4. We assume that the high-pressure water is heated up to the saturation temperature of the condensing steam. We wish to calculate the mass of steam required per unit mass of incoming liquid. The heater is assumed to be well insulated.