Aclassroom that normally contains 40 people is to be air-conditioned with window air-conditioning units of 5-kw cooling capacity. a person at rest may be assumed to dissi- pate heat at a rate of about 80 watts. there are 10 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 15,000 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. what is the source of heat being generated for the light bulbs and for the students?