4) It is commonly recommended that hot foods be cooled first to room

temperature by simply waiting a while before they are put into the

refrigerator to save energy. Despite this common-sense recommendation,

a person keeps cooking a large pan of stew three times a week and putting

the pan into the refrigerator while it is still hot, thinking that the money

saved is probably too little. But he says he can be convinced if you can

show that the money saved is significant. The average mass of the pan

and its contents is 5 kg. The average temperature of the kitchen is 23°C,

and the average temperature of the food is 95°C when it is taken off the

stove. The refrigerated space is maintained at 3°C, and the average

specific heat of the food and the pan can be taken to be 3.9 kJ/kg-°C. If

the refrigerator has a coefficient of performance of 1.5 and the cost of

electricity is $0.16/kWh, determine how much this person will save a year

by waiting for the food to cool to room temperature before putting it into

the refrigerator.