There is a vapor compression type refrigeration cycle using the refrigerant hfc 134 a. in the condenser, it is isostatically cooled, the condensation temperature is 50 ° c., and the condenser outlet is the compressed liquid at 45 ° c. in the evaporator, it is isothermally heated, the evaporation temperature is 10 ° c. and the outlet of the evaporator is heated steam at 15 ° c. when the expansion valve performs isenthalpic expansion, and the adiabatic efficiency of the compressor is 0.70, answer the following questions. (a) calculate the specific enthalpy of the compressor outlet temperature, specific enthalpy, condenser outlet and evaporator outlet. (b) obtain the cooling operation coefficient of this system. (c) obtain the circulation amount of the refrigerant necessary for obtaining the cooling effect of 3.0 kw in this system.