A tank containing 40 kg of water, initially at 40°C, has one inlet and one exit with equal mass flow rates. Water enters the tank at 40° C at the rate of 200 kg/hr. Energy is removed from the water at the rate of 8 kW by means of a cooling coil immersed in the water. The water is well mixed by a mechanical stirrer that the water temperature in the tank is uniform. The power input to the water from the stirrer is 0.3 kW. Derive an expression for the variation of water temperature in the tank with time. The specific heat of water is 4.2 kJ/kg.K. Neglect kinetic and potential energy effects.