(1 point) a computer retail store has 9 personal computers in stock. a buyer wants to purchase 4 of them. unknown to either the retail store or the buyer, 4 of the computers in stock have defective hard drives. assume that the computers are selected at random. (a) in how many different ways can the 4 computers be chosen?(b) what is the probability that exactly one of the computers will be defective?(c) what is the probability that at least one of the computers selected is defective?