Assume that you've 12 tennis balls in a black box. Each time when you go to play tennis, you randomly choose three balls one by one (assume that you cannot see the ball until you pick it out of the box and once it is taken out of the box, it will not be put back into the box until the game is over). After the game, these three tennis balls are marked as "used" if they are never marked before, and they are put back into the box. You repeat this process each time when you go to play tennis. Suppose that each ball in the box no matter which is marked or not, has the same probability to be picked. Now, it is the second time you go to play tennis. You still follow the procedure to randomly pick out three tennis balls from the box. answer the following questions
(a) Determine the probability that the second ball you pick from the box is marked?
(b) Determine the probability that all three balls you picked are never used?
(c) Determine the probability that only one ball out of three balls is marked?