Problem Only (100 points) - Consider a process to produce species B via the reaction A(gas) + (solid) -- B(gas). The reaction is carried out in a sphere whose inner surface is coated with the solid reactant species S. The bulk of the gas phase is well mixed with a uniform species A mole fraction Xao. The rate- controlling step of the process is diffusion of species A from the bulk of the gas through a stagnant layer near the inner sphere surface that extends from r=aR to r = R (where R is the inner radius of the sphere and the parameter a is a number that is less than one (a