A vapor-compression refrigeration system, using ammonia as the working fluid, has condenser and evaporator pressures of 200 psia and 30 psia, respectively. The refrigerant passes through each heat exchanger processes with negligible pressure drop. At the inlet and exit of the compressor, the temperatures are 10°F and 300°F, respectively. The heat transfer rate from the fluid passing through the condenser is 4.2 tons, and the liquid exits at 200 psia and 90°F. Assuming an adiabatic compressor, determine: (a) the compressor power; and (b) the coefficient of performance.