An emerging area of biotechnology called tissue engineering develops new processes to grow organized living tissues of human or animal origin. Living tissues require oxygen to stay alive; therefore, the mass transport of oxygen to the tissue is an important design consideration. We can model the oxygen diffusion into the tissue as a rectangular slab, where the top and bottom of the slab are 100% O2 gas, the slab is made up of tissue (of height 2L), and the oxygen diffuses down into the tissue at steady state (down if we only consider the top half what we suggest doing here). The tissue consumes oxygen with a zeroth order rate equation described by RA = k where RA is the molar rate of oxygen consumption per unit slab volume. Start with a shell balance on oxygen to derive the analytical solution for C_O2(z). (Assume the concentration of O2 at the surface is CA,s).