A Web site uses ads to route visitors to one of four landing pages. The probabilities for each landing page are equal. Consider 20 independent visitors and let the random variables W, X, Y , and Z denote the number of visitors routed to each page.

Calculate the following:

(a) P(W = 5, X = 5, Y = 5, Z = 5)

(b) P(W = 5, X = 5, Y = 5, Z = 5)

(c) P(W = 7, X = 7, Y = 6 Z = 3)

(d) P(W = 7, X = 7,Y = 3 Z = 3)

(e) P(W ≤ 2) 

(f) E(W)

(g) P(W = 5,X = 5) 

(h) P(W = 5| X = 5)