A person turns on a 100-W fan before he leaves the warm room at 100 kPa, 30oC,

Question:

A person turns on a 100-W fan before he leaves the warm room at 100 kPa, 30oC, hoping that the room will be cooler when he comes back after 5 hours. Heat transfer from the room to the surroundings occur at a rate of 5t (t in minutes) watts. Plot the change in energy of the air in the room, in kJ.