8.6 Let N denote the number of times that an asymmetric random walk that takes a step to the right with probability p and a step to the left with probability q 5 1 2 p revisits its starting point. Show that the PMF of N is given by pNðnÞ 5 P½N 5 n 5 βð12βÞ n n 5 0; 1; ... where β 5 jp 2 qj.