The diffusion equation is valid when many elementary steps are taken in the time interval of interest,

Question:

The diffusion equation is valid when many elementary steps are taken in the time interval of interest, but the random walk calculation lets us discuss distributions for short times as well as for long. Use eqn 21.84 to calculate the probability of being six paces from the origin (that is, at x= 61) after
(a) Four,
(b) Six,
(c) Twelve steps.