4) [25 pt] Compound A diffuses through a 4-cm-long tube and reacts as it diffuses. The equation governing diffusion with reaction is, for concentration given by A : Ddx2d2AkA=0 At one end of the tube (x=0), there is a large source of A that results in a fixed concentration of 0.1M. The other end of the tube is impenetrable to species A, so the boundary condition is dA/dx=0 at x=L= 4cm. Using the finite difference method with nodes every 0.4cm, calculate A as a function of distance in the tube. Compare the results with k=5106s1 and D=1.5106,6.0106 and 12106cm2/s