A shelf in the Metro Department Store contains 85 colored ink cartridges for a popular ink-jet printer. Seven of the cartridges are defective.
(a) If a customer selects 2 cartridges at random from the shelf, what is the probability that both are defective? (Round your answer to five decimal places.)
(b) If a customer selects 2 cartridges at random from the shelf, what is the probability that at least 1 is defective? (Round your answer to three decimal places.)
(a) 7/85 * 6/84
(b) 1 - P(0 defective) = 1 - 78/85 * 77/84