Q$\mathrm{.}4.$ A carnot refrigrator has working tempr.

a$)$ of $-30C$ and $35C.$ If it operated with RH as a working substance, Calculate the work of isentropic compression and that of isentropic expansion, and refrigrating effect, heat rejected per kg of refrigrant and COP of the cycle.

b$)$ If the actual refrigrator operating on the same tempr has a cop of $0\mathrm{.}75$ of the maximum, calculate the power consumption and heat rejected to the surroundings per ton of refrigration.