Species A, which is present in dilute concentration, is diffusing at steady state from the bulk of the fluid through a stagnant film of B of thickness to the external surface of the catalyst. The reaction takes place is A2B. The concentration of A at the external boundary is C Ab and at the catalyst surface is CAs, with Cab > Cas. Determine the concentration profile and the flux of A to the surface using (a) shell balance, and (b) the general balance equation. (DAB = 0.01 cm2/s, C To = 100 mol/m3 , yab = 0.9, y As = 0.2)