Steam enters a closed feedwater heater at 1.1 MPa, 200oC and leaves as saturated liquid at the same pressure. Feedwater enters the heater at 2.5 MPa, 50oC and in an isobaric manner leaves 12oC below the exit temperature of the steam. Neglecting any heat losses, determine (a) the mass flow rate (m) ratio and (b) the exergetic efficiency of the heat exchanger. Assume surroundings to be at 100 kPa and 25oC.