Consider a single, porous, spherical, inert mineral particle. The pores inside the particle are filled with liquid water (species B). We are interested in analyzing the molecular diffusion of the contaminant benzene (species A) within the water filled pores of the particle. Benzene is very sparingly soluble in water, and does not adsorb onto the inter surfaces of the pores. The process is isothermal at 298 K. The concentration of dissolved benzene in the water surrounding the particle is constant with time. Starting with the general differential equation for mass transfer, develop the differential equation to describe the concentration profile of benzene within the single, porous, spherical, inert mineral particle. The effective diffusion coefficient of benzene in the water-filled pores of the particle is represented by the term D_Ae. As part of the analysis, state all reasonable assumptions, as well as boundary/initial conditions for the process.