Ben Watson found $25,000 lying on the sidewalk and decided to invest the money. He believes that he can earn a 10 percent rate (compounded annually) on his investment for the first four years, 12 percent for the following three years, and 15 percent for the following five years.

a. How much money will Ben have at the end of four years, seven years, and twelve years?

b. If someone offered to pay him $36,000 at the end of four years for the $25,000 should he accept? Why or why not?