Because of a mistake in packaging, a case of 15 bottles of wine contained 9 of brand A and 6 of brand B, each without labels. All the bottles look alike and have an equal probability
of being chosen. Four bottles are randomly selected.
(a) What is the probability that all four are brand A?
(b) What is the probability that exactly one is brand A?
(c) What is the probability that none is brand A?