8 An internally reversible refrigerator has a modified coefficient of performance accounting for realistic heat transfer processes of where qin is the refrigerator cooling rate, qout is the heat rejection rate, and is the power input. Show that COPm can be expressed in terms of the reservoir temperatures Tc and Th, the cold and hot thermal resistances Rt, c and Rt, h, and qin, as where Rtot Rt, c Rt, h. Also, show that the power input may be expressed as