In a foundry, metal castings are cooled by quenching in an oil bath. Typically, a casting weighing 20 kg and at a temperature of 450^◦C is cooled by placing it in a 150-kg involatile oil bath initially at 50^◦C. If C_P of the metal is 0.5 J/(kg K), and C_P of the oil 2.6 J/(kg K), determine the common final temperature of the oil and casting after quenching if there are no heat losses. Also, find the entropy change in this process.