the transient concentration profile ca(z,t) resulting from transient one-dimensional diffusion in a slab under conditions of negligible surface resistance is described by equation (27-16). use this equation to develop an equation for predicting the average concentration, ca, within the control volume at a given time t. then evaluate and plot the dimensionless average profile ca cas / cao cas as a function of the dimension- less relative time ratio, xd. use a spreadsheet to perform the calculations needed to implement the infinite series analytical solution.