Ashelf in the metro department store contains 85 colored ink cartridges for a popular ink-jet printer. six of the cartridges are defective.
(a) if a customer selects 3 cartridges at random from the shelf, what is the probability that they are all defective? (round your answer to five decimal places.)

(b) if a customer selects 3 cartridges at random from the shelf, what is the probability that at least 1 is defective? (round your answer to three decimal places.)