In Problem use probability trees to find the probabilities of the indicated outcomes.
An urn contains 4 red, 5 white, and 6 black balls. One ball is drawn from the urn, it is replaced, and a second ball is drawn.
(a) What is the probability that both balls are white?
(b) What is the probability that one ball is white and one is red?
(c) What is the probability that at least one ball is black?