Hot water traveling through a thick-walled steel pipe (k=60 W/m·K) is cooled externally by a cross-flow airstream at a velocity of 20 m/s at a temperature of 25ºC. The inner and outer diameters of the pipe are Di=20 mm and Do=25 mm. The hot water enters at 90ºC at a mass flow rate of 0.11 kg/s. What is the mean temperature of the water exiting the 20 meter long pipe? Assume that the entire flow is hydrodynamically and thermally fully-developed.