i cant decide which one is cold sink or hot one. should i consider coil-house and coil-outside are different carnot engine?

8. A heat pump is to be installed in a house to maintain the indoor temperature in summer at 25C. If the amount of heat required for summer cooling is 80 kJ.s-1, the refrigerant is circulated to 5C in the summer through the internal exchange coil, the underground temperature used as the heat sink is maintained at 15C, and the temperature of the refrigerant is 25C due to the characteristics of the coil, the amount of power required for summer cooling [kW]. 1 0.29 2 4.00 3 5.75 4 32.0