A house has a winter heating requirement of 30 kJ/s and a summer cooling requirement of 60 kJ/s. Consider a heat-pump installation to maintain the house temperature at 20 °C in the winter an 25 °C in the summer. This requires circulation of the refrigerant through interior exchanger coils at 30 °C in the winter and 5 °C in the summer. Underground coils provide the heat source in the winter and the heat sink in the summer. For a year- round ground temperature of 15 °C, the heat transfer characteristics of the coils necessitate refrigerant temperatures of 10 °C in winter and 25 °C in summer. What are the minimum power requirements for winter heating and summer cooling?