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A cross flow heat exchanger is used to heat air with water. The area is 8.4m2 and the overall heat transfer coefficient is 250W/(m2K). The air is mixed, and enters at 15C with a mass flow rate of 2.0kg/s. The water is unmixed, and enters at 90C with a mass flow rate of 0.25kg/s. The heat capacities are 1005 and 4180J/(kgK) for the air and water respectively. Calculate the rate of heat transfer and the exit temperatures of the two streams