Twenty percent of U. S. 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 exactly 15 of the mortgages are underwater? (Round your answer to 4 decimal places.) b. What is the probability that more than 20 of the mortgages are underwater? (Round your answer to 4 decimal places.) c. What is the probability that at least 25 of the mortgages are underwater? (Round your answer to 4 decimal places.)