Aroom with dimensions of 4m-by-5m-6m is to be heated by an electrical resistance heater placed in a short duct in the room. initially, the room is at 15oc and the local atmospheric pressure is 98 kpa. the room is losing heat steadily to the outside at a rate of 150 kj/min. a 200-w fan circulates the air steadily through the duct at a rate of 40 kg/min. it can be assumed that the duct operates adiabatically and there is no air leaking out or into the room. it takes 20 minutes for the average room temperature to reach 25oc. determine (a) the power supplied to the resistance heater and (b) the change in temperature of the air between the entrance and exit of the duct. (ans: (a) 3.15 kw; (b) 5 ? oc)