Diane works at a public university. She contributes $625 at the end of each month to her retirement fund. For the past 10 years, this fund has returned 3.84% a year, compounded monthly.

a. Assuming the 3.84% rate continues, how much will she have in her retirement account after 15 years?

b. Assume the economy has gotten better and that the fund now has a return of 7.72% compounded monthly. Since Diane's salary has risen over the first 15 years, she can now contribute $1000 per month. At the end of the next 15 years, how much is her account worth?