You are separating hydrogen from an air stream by a membrane. The initial concentration of hydrogen in the gas is known as xAo. The concentration on the other side of the membrane is mostly pure xAL. The membrane thickness is$.$ Inside radius is R$.$ The membrane is cylindrical depicted below. The transport through the membrane is by diffusional processes and the diffusion coefficient is known DAm.

A$)$ Show how you would set up a microscopic balance for conservation of species A in the membrane to obtain a differential equation for the concentration in the radial direction. Note that he concentration xA is small in the membrane material.

B$)$ Give an expression for the flux rate through the membrane.