An urn contains n white and m black balls, where n and m are positive numbers.
a) If two balls are randomly withdrawn, what is the probability that they are the same color?
b) If a ball is randomly withdrawn and then replaced before the second one is drawn, what is the probability that the withdrawn balls are the same color?
c) Show that the probability in part (b) is always © Show that the probability in part (b) is always larger than the one in part (a).