Suppose that a deck of n cards numbered 1, 2, .. , 20 is thoroughly shuffled and dealt. For 1 <= i <= 20, let X(i) be the number on the ith card dealt. Let C be the number of i such that 2 <= i <= n and X(i) = X(i-1) + 1.
a). Find a simple formula for E(C).
b). Find a formula for Var(C).