1.A ref system has working temp of -30'c and 40'c.what is the maximum C.O.P possible?If the actual C.O.P is 75% of the max. calculate the actual refrigerating effect produced per kwhour?

I know the fourmula of C.O.P in the case of reverse carnot cycle T2/(T1+T2) SO what is the different between actual and max COP. What is the atual refrigerating effect produced per hour fourmula. pls send the answer in my email id wrik.chakraborty@yahoo.com.
TY SIR