6.71 Refrigerant 22 enters the heat exchanger of an air-conditioning system at 80 lbf/in. with a quality of 0.2. The refrigerant stream exits at 80 lbf/in., 60F. Air flows in counterflow through the heat exchanger, entering at 14.9 lbf/in., 80F, with a volumetric flow rate of 100,000 ft/min and exiting at 14.5 lbf/in., 65F. Operation is at steady state, stray heat transfer from the outside of the heat exchanger to the surroundings can be neglected, and kinetic and potential en- ergy effects are negligible. Assuming ideal gas behavior for the air, determine the rate of entropy production in the heat exchanger, in Btu/min R.