In a single-pass cross-flow heat exchanger, engine oil (unmixed) enters the tube bank at 80C with a total mass flow rate of 1.5 kg/s. It is used to heat up water (mixed) flowing in the shell across the unfinned tubes at 0.8 kg/s from 25C to 50C. Determine: a) the exit temperature of the engine oil; (6 marks) b) the log mean temperature difference of the heat exchanger. (6 marks) c) Assuming that the overall heat transfer coefficient of the heat exchanger is 150 W/mK, determine the total heat transfer area required. (7 marks) d) If the tube bank consists of thin-walled tubes of 10 rows high and 20 rows deep, with each tube having a diameter of 20 mm, determine the required length of each tube for the heat exchanger. (6 marks) You may assume that the specific heat capacities of the engine oil and the water are constants at 2.1 kJ/kg.K and 4.2 kJ/kg.K respectively.