A4-m × 5-m × 7-m room is heated by the radiator of a steam-heating system. the steam radiator transfers heat at a rate of 10,000 kj/h, and a 100-w fan is used to distribute the warm air in the room. the rate of heat loss from the room is estimated to be about 5000 kj/h. if the initial temperature of the room air is 10°c, determine how long it will take for the air temperature to rise to 20°c. assume constant specific heats at room temperature.