50kg of water at 0ºC have to be frozen into ice in a refrigerator. The room temp. is 20ºC. What is the minimum work input to the refrigerator to achieve this? (latent heat of fusion of water=3.33x10^5J/kg) ans:1.22x10^6J It is proposed to heat a house using a heat pump operating between the house and the outside. The hose is to be kept at 22ºC, the outside is at -10ºC and the heat loss from the house is 15kW. What is the minimum power required to operate the pump? ans:1.63kW Please help me to show the methods. I don't understand!!