A heat pump is used to heat a house in the winter and to cool it in the summer. During the winter, the outside air serves as a low -temperature heat source; during the summer, it acts as a high-temperature heat sink. The heat-transfer rate through the walls and roof of the house is 0.75 kJ s-1 for each C of temperature difference between the inside and outside of the house, summer and winter. The heat-pump motor is rated at 1.5 kW. Determine the minimum outside temperature fur which the house can be maintained at 20 C during the winter and the maximum outside temperature for which the house can be maintained at 25°C during the summer.