Consider the evaporator section of a window air conditioner (note: the evaporator may be considered as a shell and tube heat exchanger with refrigerant flowing through the tube and air flowing through the shell). Air enters the evaporator at 14.7 psia and 90±F with a volumetric flow rate of 200 ft3/min. Refrigerant 134a at 20 psia with a quality of 30% enters the evaporator at a rate of 4 lbm/min and leaves as saturated vapor at the same pressure. Assume steady state operation and negligible pressure changes through the evaporator. Also, assume the air behaves as an ideal gas with constant specific heats. Determine:
a. the rate of heat transfer from the air [Btu/min]
b. the exit temperature of the air [F]