A refrigerator using R-134a as the working fluid operates on an ideal vapor compression refrigeration cycle between 0.15 MPa and 1 MPa. If the mass flow rate is 1 kg/s, determine (a) the net power necessary to run the system and (b) the COPR. (c) What-if Scenario: What would the COP be if the expansion valve were replaced with an isentropic turbine?