Ashell-and-tube heat exchanger with two shell passes and eight tube passes exchanges heat between water and hot air. the air flows in the shell, entering with a temperature of 350°c and leaves the heat exchanger at 175°c. water flows in the tubes at the rate of 45,500 kg/hr., entering with a temperature of 80°c and leaving at 150°c. the total surface area for the heat exchange is 925 m2. if the specific heat of water is 4,236 j/kg °c, calculate the overall heat transfer coefficient.