A household refrigerator that has a power input of 450 W and a COP of 1.500 is to cool five large watermelons, 10 kg each, to 8C. If the watermelons are initially at 28C, determine how long it will take for the refrigerator to cool them. The watermelons can be treated as water whose specific heat is 4.2 kJ/kg-C. Is your answer realistic or optimistic? The time taken for the refrigerator to cool the watermelonsis[ ] min and the answer is