A 40 student class is to be air conditioned with window air conditioning units each with 5 kw cooling capacities. a student at rest is assumed to dissipate heat at a rate of 360 kJ/h. there are 10 light fixtures in the room, each with a rating of 100 W. the rate of heat transfer into the class room through the walls and the windows is estimated to be 15000 kJ/h. if the room air temperature needs to be maintained at a constant 21 C how many window air conditioning units are required.