Problem 1 (35 points): A shell-and-tube heat exchanger consists of 135 thin- walled tubes in a double-pass arrangement, each of 12.5-mm diameter with a total surface area of 47.5 m2. Water (the tube-side fluid) enters the heat exchanger at 15 C and 6.5 kg/s and is heated by exhaust gas entering at 200 C and 5 kg/s. The gas may be assumed to have the properties of atmospheric air, and the overall heat transfer coefficient is approximately 200 W/m2K. What are the gas and water outlet temperatures?

please start with assumptions