A bag contains 5 blue, 6 red, and 9 green marbles. How many marbles must be drawn from the bag without looking to be sure that we have drawn (a) a pair of blue marbles? (b) a pair of marbles of the same color? (c) a pair of marbles of different colors? (d) three marbles of the same color? (e) a blue marble, a red marble, and a green marble?