Hot refined oil at 120 °C enters a concentric tube-in-tube heat exchanger (HE) at the rate of 20 kg min⁻¹. The oil is cooled by water entering at a temperature of 30 °C from the other end of the HE at the rate of 50 kg min⁻¹. Specific heat capacities of oil and water are 1.9 and 4.2 kJ kg⁻¹ °C⁻¹, respectively. The effectiveness of the HE may be taken as 0.7. Assuming no heat loss to the surrounding under steady-state condition, the exit temperature of water from the HE in °C is