In the manufacture of tablet blister packs of a drug, 5% of the blister packs are defective. We choose n blister packs at random for quality control. (a) Assume that n = 25 blister packs are checked. What is the probability that at least one platelet is defective? (b) Of n = 25 wafers, what is the expected number of defective wafers? (c) How many wafers must be selected in order to be 90% certain of having at least one faulty wafer? (c) How many wafers must be selected in order to be 90% certain of having at least one defective wafer among the n selected wafers?