A gas refrigeration cycle with a pressure ratio of 3 uses helium as the working fluid. The temperature of teh helium is -10 degrees celsius at the compressor inlet and 50 degrees celsius at the turbine inlet. Assuming isentropic efficiencies of 80 percent for both the turbine and the compressor, determine (a) the minimum temperature in the cycle, (b) the coefficient of performance, and (c) the mass flow rate of 18 kW