15. A 5 kg piece of lead (specific heat 0.03 cal/g C°) having a temperature of 80° C is added to 500 g of water having a temperature of 20°. What is the final equilibrium temperature in °C of the system?
(A) 79
(B) 26
(C) 54
(D) 34

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統計： A(1), B(1), C(2), D(1), E(0) #347702