This question is killing me because I just can't seem to get it. A heat pump is used to heat a house in winter; the inside radiators are at T_h and the outside heat exchanger is at T_c. If it is a perfect (e.g., Carnot cycle) heat pump, what is K_pump, its coefficient of performance? Give your answer in terms of T_h and T_c. According to the hints, you're meant to work out the efficiency of the pump in terms of Q_c and Q_h. I thought it was 1 + (Q_c/Q_h)... The textbook states that Q_c/Q_h = - T_c/T_h, but in the hints, it states Q_h/Q_c = T_h/T_c. I'm totally confused. Please help.