Use to find each of these probabilities:
(a) The probability that exactly two defective welds and one improperly tightened bolt will be produced by the robots.
(b) The probability that at least one defective weld and at least one improperly tightened bolt will be produced.
(c) The probability that at most one defective weld will be produced.
(d) The probability that at least two improperly tightened bolts will be produced.