A number, denoted by X1> is chosen at random from the set of integers {I, 2, 3, 4}. A second number, denoted by X2, is chosen at random from the set {1, 2, ... , X1}.
(i) For each integer k, 1 to 4, find the conditional probability that X2 = 1, given that X1 = k.
(ii) Find the probability that X2 = 1.
(iii) Find the conditional probability that X1 = 2, given that X2 = 1.