Probability Question?

At the charity event, four lucky door prizes are to be awarded. The 400 guests each write their names on
a ticket which is placed in the draw. There are 100 red tickets, 100 green tickets, 100 yellow tickets and
100 blue tickets. The four winning tickets are drawn at the same time.
(a) What is the probability that all four winning tickets are red?
(b) What is the probability that at least one of the winning tickets is not red?
(c) What is the probability that there is one winning ticket of each color?