There are 20 families living in the Willbrook Farms Development. Of these families, 10 pre- pared their own federal income taxes for last year, 7 had their taxes prepared by a local professional, and the remaining 3 by H&R Block.

a. What is the probability of selecting a family that prepared their own taxes?

b. What is the probability of selecting two families, both of which prepared their own taxes?

c. What is the probability of selecting three families, all of which prepared their own taxes?

d. What is the probability of selecting two families, neither of which had their taxes pre- pared by H&R Block?