Question

Before leaving for a vacation£¬the owners of a home 8.0m *21m*5.0m turn the thermostat down to 14celcius. On their return£¬how much heat is needed to raise the temperature of the air inside the home to 21celcius£¿Ignore the heat needed to warm the walls and the contents of the house.The density of air is 1.3kg/m3.