Consider a long cylinder of porous material of radius R in which a gas A is being generated throughout the cylinder at a rate of RA [moles of A/ft3 hr] and is diffusing through the porous material. The concentration of A at the surface of the porous cylinder is XAR. Derive the differential equation to find the mole fraction of A in the cylinder as a function of radial position. Solve the differential equation to find the mole fraction of A as a function of position.