7. (8 points) A heat pump heats the air in a rigid, insulated cuboid room of size 25m x 10m x4m. The heat pump consumes 15 kW of power. The initial temperature and pressure in this room are 12 °C and 1 bar, respectively. With an average coefficient of performance of COPHP= 3.0over the range of air temperature in this room, how long will it take to heat the air in this room from 12 to 27 °C?

Fig: 1