28. The pmf for X  the number of major defects on a randomly selected appliance of a certain type is x 0 1 2 3 4 p(x) .08 .15 .45 .27 .05 Compute the following:

a. E(X)

b. V(X) directly from the de nition

c. The standard deviation of X

d. V(X) using the shortcut formula