Consider a vertical pipe through which humid air flows. The pipe is kept at 5 oC, which is cooler than the air and, importantly, below the 8 oC dew point of the air. As a result, water condenses on the inner walls to maintain a thin layer of liquid water. Though the water layer would eventually get thick enough that it would fall due to gravity, you can neglect that here. a. Draw a picture of the physical system, select the coordinate system that best describes the transfer process, and state at least five reasonable assumptions of the mass-transfer aspects of the process. b. What is the simplified form of the general differential equation for mass transfer in terms of the flux of water vapor, NA? c. What is the simplified differential form of Ficks flux equation for water vapor? d. What is the simplified form of the general differential equation for mass transfer in terms of the molar concentration of water vapor, cA?