The irreversible first-order (wrt partial pressure of a) gas-phase reaction a → b is carried out isothermally in a "fluidized" catalytic cstr containing 50 kg of catalyst. currently, 50% conversion is realized for pure a entering at a pressure of 20 atm. there is virtually no pressure drop in the cstr. it is proposed to put a pbr containing the same catalyst weight in series with the cstr. the pressure drop parameter for the pbr, α, given by equation (5-29) is α = 0.018 kg–1. the particle size is 0.2 mm, the bed porosity is 40%, and the viscosity is the same as that of air at 200°c. (a) should the pbr be placed upstream or downstream of the cstr in order to achieve the highest conversion? explain qualitatively using concepts you learn