Assume that 25-year-old Denise wastes $10 per week buying lottery tickets, averaging $520 per year. Now let's assume that Denise "sees the light" and decides to take that $520 she would have spent on lottery tickets and deposit it at the end of each year in an annuity paying 6% compounded annually.

a. How much would Denise have in this annuity after 20 years?

b. Find the interest her money has earned during that 20 years.