The steel product was hardened by heating to a temperature tst = 800°C, followed by lowering a mass mm = 2 kg into oil, taken at a temperature tm = 10°C. At the same time, the oil was heated to a temperature Q = 40°C. Find the mass mst of the steel product if, when transferred to oil, the product was cooled to dt = 20°C. Specific heat capacity of steel cst = 0.63 kJ/(kg K), oil cm = 1.9 kJ/(kg K).

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