The seeds of the garden pea (Pisuin sativum) are either yellow or green. A certain cross between

Question:

The seeds of the garden pea (Pisuin sativum) are either yellow or green. A certain cross between pea plants produces progeny in the ratio 3 yellow: 1 green. If four randomly chosen progeny of such a cross are examined, what is the probability that
(a) Three are yellow and one is green?
(b) All four are yellow?
(c) All four are the same color?