2. [2 points] A biofilm is a layer-like aggregation of microscopic organisms, plant or bacteria attached to a solid surface. In many natural aquatic systems, especially those having a high specific surface area and low nutrient concentrations, biofilms are 90% to 99.9% bacteria. Biofilms are found in or on stream-beds, ground-water aquifers, water pipes, ship hulls, piers, and aquatic plants and animals. Engineered processes that utilize films of bacteria include trickling filters, biologically activated carbon beds, and land treatment systems. Sometimes the biofilm can shield a surface undergoing a reaction, i.e., protection against corrosion. For simplicity, here we will consider such a biofilm where the reactant is consumed only at the solid surface, maintaining a particular value of surface concentration. Consider a case where the biofilm thickness is 0.01 cm and the diffusivity of the reactant is 0.8 cm/day. The reactant concentration in the bulk liquid is uniform at 3.2 mg/L, while the reactant concentration at the surface is 0.25 mg/L. a. Calculate the concentration profile of the reactant in the biofilm at steady state. b. Calculate the reactant flux.