Oil in an engine is being cooled by air in a cross-flow heat exchanger, where both fluids are unmixed. oil (cp = 2000 j/kg. k) flowing with a flow rate of 0.020 kg/s enters the heat exchanger at 75°c, while air (cp = 1000 j/kg. k) enters at 30°c with a flow rate of 0.20 kg/s. the overall heat transfer coefficient of the heat exchanger is 50 w/m2 . k and the total surface area is 1 m2 . determine: (a) the heat transfer effectiveness and (15 points) (b) the outlet temperature of the oil. (use the effectiveness-ntu method) (15 points)