Watermelons are a great treat in the summer. In hot weather, watermelons are even more enjoyable chilled. (a) Assume that you have a 15-lb watermelon and need to cool it down from the outside temperature (90F) to the temperature of the refrigerator's interior (40F). Your household refrigerator has a coefficient of performance (COP) of 3.5, and the cost of electricity is $0.12 per kWhr. 

How much electrical energy (in kJ) would the refrigerator consume to cool the watermelon and how much would it cost you (in US cents). Assume that the watermelon has the same specific heat as water. 

(b) How much extra would it cost to remove this additional amount of heat from your house using a central air conditioning system with a COP of 3? What is the total cost of electricity for running the fridge from part (a) and the air conditioner?

(c) How much money would you save by allowing the watermelon to cool down to room temperature of 70F before putting it into the refrigerator? Do not forget about the