Computer keyboard failures can be attributed to electrical defects or mechanical defects. A repair facility currently has 25 failed keyboards, 6 of which have electrical defects and 19 of which have mechanical defects. (a) How many ways are there to randomly select 5 of these keyboards for a thorough inspection (without regard to order)? ways (b) In how many ways can a sample of 5 keyboards be selected so that exactly two have an electrical defect? ways (c) If a sample of 5 keyboards is randomly selected, what is the probability that at least 4 of these will have a mechanical defect? (Round your answer to four decimal places.)