A vapor-compression refrigeration system is conventional except that a counter-current heat exchanger is installed to subcool the liquid from the condenser by heat exchange with the vapor stream from the evaporator. The minimum temperature difference for heat transfer is 5 degrees Celcius. Hexafluoroethane is the refrigerant R-116, evaporating at -6 degrees Celcius and condensing at 26 degrees Celcius. The heat load on the evaporator is 2000 kJ/s. If the compressor efficiency is 75%: a) what is the power requirement? b) How does this result compare with the power required by the compressor if the system operates without the heat exchanger? c) How does the refrigerant circulation rates compare for the two cases?