100 kg/h of milk is heated in a heat exchanger 45c to 72c. water is used as the heating medium. It enters the heat exchanger at 90c and leaves at 75c. 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 given equal to 4.2 kJ/kg and that of milk 3.9 kJ/kg