A cold air-standard Brayton refrigeration cycle has a pressure ratio of 4 and a refrigeration rate of 15 kW. Air enters the compressor at -7oC. The high pressure air is cooled to 27 oC by rejecting heat to the surroundings. It is further cooled to -15oC by regenerative cooling before entering the turbine. Assuming constant specific heat at room temperature, Determine:
a) The minimum temperature of the cycle (oC)
b) Coefficient of performance
c) Mass flow rate of air (kg/s)