1000 kg/h of milk is heated in a heat exchanger from 45oC to 72oC. Water is used as the heating medium. It enters the heat exchanger at 90oC and leaves at 75oC. Calculate the mass flow rate of the heating medium, if the heat losses to the environment are equal to 1 kW. The heat capacity of water is given equal to 4.2 kJ/kgoC and that of milk 3.9 kJ/kgoC.