A 4m x 5m x 7m room is heated by the radiator of a steam heating system. The radiator transfers heat at a rate of 10000KJ/hr, a 100 w fan is used to distribute the air in the room. The rate of heat loss from the room is 5000KJ/hr. If the initial temperature of air in the room is 10 degrees celcius determine how long it will take for the air to rise to 20 degrees celcius. Assume constants specific heats at room temperature. ans is 831 sec.