A non$-$ideal vapor$-$compression refrigeration cycle using HFC$-134$a as the working fluid operates at an evaporator temperature of $-15$C and a condenser pressure of $1$ MPa. Saturated vapor enters the compressor and saturated liquid exits the condenser. If the isentropic efficiency of the compressor is $0\mathrm{.}90,$ and the refrigerant flow rate is $1$ kg$/$min$,$ find a$)$ The coefficient of performance of the cycle b$)$ The power input to the compressor $($in kW$)$