A health safety comittee is to be selected from all the people who work at at a local factory. The committee is to consist of four members selected randomly from a list of ten names submitted by the shop leader. The list has the names of five union members and five workers who are not union members.

a) What is the probability that the first person selected from the list is a union member. 1/2

b)What is the probability that the first 2 people selected from the list are union members. 5/10 x 4/9 (tree diagram)=2/9

c)What is the probability that all commitee members are union members. 1/42 (used a tree diagram).

d)What is the probability that three of the four committee members are union members.

I dont know how to get this answer...