4. The spherical catalyst shown in the sketch is being used to catalyze the first-order reaction, AB, with a reaction rate, Rav=kCA. Analyze the problem as simultaneous molecular transport and chemical reaction in a porous sphere and (a) Solve for the concentration of "A" within the catalyst. [HINT: The differential equation can be solved by making the substitution CA=r and then use the total derivative for =f(C,r)]