Problem:
Jane's goal is to have an investment grow to $100000 in 20 years. Her strategy is to make lump-sum contributions in years 0, 5, 10, and 15. That is, in Year 0, she will contribute $X, in year 5 she will contribute $x, etc. where $X is the same at each contribution. Earning an effective annual rate of interest of 10%, what does she need to contribute at each payment to meet her goal?