From the set {1, 2, 3,... , n}, k distinct integers are selected at random and arranged in numerical order (from lowest to highest). Let P(i, r, k, n) denote the probability that integer i is in position r. For example, observe that P(1, 2, k, n) = 0, as it is impossible for the number 1 to be in the second position after ordering.
(a) Compute P(2, 1, 6, 10).
(b) Find a general formula for P(i, r, k, n).