Consider porous catalyst particles in the shape of thin disks, such that the surface area of the edge of the disk is small in comparison with that of the two circular faces. The catalyst reacts with a gas A with first order kinetics with a rate constant �! per unit surface area. The disk surface is exposed to a concentration of �"# which is held constant and the available surface area per unit volume is �. The rate of reaction �" per unit volume is given as �" = −�!��". (a) Show that the steady state concentration profile of A inside the disk is