Question: Counting/grading

One professor grades homework by randomly choosing 5 out of 12 homework problems to grade.

a) How many different groups of 5 problems can be chosen from the 12 problems?

b) Probability extension-Jerry did only 5 problems of one assignment. What is the probability of the problems he did comprised the group that was selected to be graded?

c) Silvia did 7 problems. How many different groups of 5 did she complete? What is the probability of one of the groups of the 5 she completed comprised the group that was selected to be graded?