Problem #2: Like the Heat equation, non-steady state mass transfer equation which is also a parabolic equation can be used to estimate the concentration of a pollutant in a river. If only considering the diffusion effect, the concentration of the pollutant in the river, GC(x, t), satisfies the equation: DCx+f(x,t) Where D is the diffusion rate. Assume we reduce the equation into non-dimensional form(0 x S 1). Suppose at x 0, the pollutant(e.g. lead) concentration equals to l ; at x = 1, the pollutant concentration reduced to 0.001. At t 0, the initial concentration of lead is 0.001. Let the right end of the temporal interval equals to 0.1. Let D 1.0 and f(x,t)0. Compute and plot the lead concentration as a surface plot using Heatl(forward method) function provided on CCLE and the surf command in MATLAB and for a) nx = 20, nt = 80 b) nx = 20, n.-77 For both cases, find out the concentration of lead at x = 0.5, t = 0.1. Describe the figures and compare the concentration of lead at this specific location and time for these two cases