1. UNDERWATER MORTGAGE

Twenty percent of US mortgages are "underwater" (The Boston Globe, March 5, 2009). A mortgage

is considered underwater if the value of the home is less than what is owed on the mortgage.

Suppose 100 mortgage holders are randomly selected.

a) What is the probability that more than 20 of the mortgages are underwater?

b) What is the probability that at least 25 of the mortgages are underwater?