3. (30 points) An elemenlary isemerization reaction of AB is carried out in a differential reactor containing catalysts with planar geometry. In one experiment, a catalyst poison P entered the reactor together with reactant A. If the poison renders the catalyst pore walls near the pore mouth ineffective up to a distance Lt from the center of the pore (z=L, to z=L1), so that no reaction takes place in this entry region (See Figure below). 0