Starting at value 0, the profit of an investor increases per week by one unit with probability p, p > 1/2, or decreases per week by one unit with probability 1 − p. The weekly increments of the...

Starting at value 0, the profit of an investor increases per week by one unit with probability p, p > 1/2, or decreases per week by one unit with probability 1 − p. The weekly increments of the investor's profit are assumed to be independent.

Let N be the random number of weeks until the investor's profit reaches for the first -time a given positive integer n. By means of Wald's equation, determine E(N).