The manufacture of tablet inserts of a medicine, 5% of the platelets are defective. N platelets are chosen at random for quality control. (a) Assume that n = 25 platelets are verified. What is the probability that at least one platelet is defective?

b) Among n = 25 platelets, what is the expected number defective platelets? (c) How many plates must be selected in order to be 90% certain of having at least one platelet being defective within n selected platelets