The temperature of the engine oil of a diesel engine needs to be reduced from 95 oC to 70 oC. A cross-flow heat exchanger (HE) is used for this purpose. The engine oil flows through the tubes which are arranged in a 7 x 7 array. Water is used as a coolant which flows over the tube array. The water enters the HE at a mass flow rate of 2.22 kg/s and exits at 33 oC. The mass flow rate of the engine oil is 1.5 kg/s. The specific heats of the oil and water are 1.9 kJ/kgK and 4.18 kJ/kgK, respectively, and the convective HT coefficients are 1,000 W/m2K and 1300 W/m2K, respectively. If the tube diameter is 1 cm (ignore its wall thickness), determine the length of the tube bank