a company orders supplies from 10 distributor and wishes to place 7 orders. what is the probability that

a. all the orders go to different distributors

b. distributor 1 gets 2 orders and distributor 2 gets 3 orders

c. distributor 1,2,3 gets 2,3,1 orders respectively?

sorry, im really bad at probability...not sure how to approach such questions..

thanks!