6–49 A household refrigerator that has a power input of 450 W and a COP of 1.5 is to cool 5 large watermelons, 10 kg each,to 8°C. If the watermelons

are initially at 28°C, 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? Explain. Answer: 104 min