A box contains 6 pagers. Assume any pager selected from the box is done randomly, and hence
selections are independent from each other. The probability of a selected pager being defective is 0.25.
Let X be the random variable for the number of defective pagers.
(a) Determine the probability of selecting exactly 2 defective pagers.
(b) Determine the probability of seleecting at least 5 defective pagers.
(c) Determine the mean and variance of X