A counter shell and tube exchanger is used to heat water with hot exhaust gases.the water (C=4180 J/kg c)flows at a rate 2 kg/s while the exhaust gas (1030 J/kg c)flows at rate of 5.25 kg/s. If the heat transfer surface area is 32.5 and overall heat transfer coefficient is 200 what is NTU for the heat exchanger.