A box consists of five green balls, three black balls and seven red balls. Two balls are selected without replacement from the box. (a) What is the probability that both balls are the same color? (b)...

A box consists of five green balls, three black balls and seven red
balls. Two balls are selected without replacement from the box.
(a) What is the probability that both balls are the same color?
(b) Given that both balls are the same color, what is the probability that they are
black?