I need help with this exercise. I don't understand what probability rule I have to used with it.

Because of a mistake in packaging, a case of 12 bottles of red wine contained 5 Merlot and 7 Cabernet, each without labels. All the bottles look alike and have an equal probability of being chosen. Three bottles are random selected.

a) What is the probability that all 3 are Merlot?

b) What is the probability that exactly two are Merlot?

c) what is the probability that none is a Merlot?