A counterflow, concentric tube heat exchanger is designed to heat water from 20 to 80o C using hot oil, which is supplied to the annulus at 160o C and discharged at 140o C. The thin-walled inner tube has a diameter of DI = 20 mm and the overall heat transfer coefficient is 500 W/(m2 K). The design condition calls for a total heat transfer rate of 3000 W. (a) what is the length of the what exchanger? (b) After