Aclassroom that normally contains 27 people is to be air conditioned with window air-conditioning units of 7.5-kw cooling capacity. a person at rest may be assumed to dissipate heat at a rate of about 375 kj/h. there are 14 lightbulbs in the room, each with a rating of 100 w. the rate of heat transfer to the classroom through the walls and the windows is estimated to be 14,500 kj/h. if the room air is to be maintained at a constant temperature of 21°c, determine the number of window air-conditioning units required.