Combustion gases passing through a 3 cm internal diameter circular pipe are used to vaporize waste water at atmospheric pressure. hot gases enter the pipe at 250 c at a mean velocity of 5 m/s, and leave at 150°c. if the average heat transfer coefficient is 40 w/m2-k and the inner surface temperature of the pipe is 110°c, determine the surface area of the pipe. (ρ = 0.7662 kg/m, cp=1023 j/kg-k) a. 0.012 m2 b. 0.035 m2 0.061 m2 c. d. 0.087 m2