Sam's grandparents have offered to help pay for some of her university expenses. Sam will receive $5,000 each for year of study, with the payments received at the start of each school year. How much will her grandparents have to invest today to make four annual (start-of-year) payments? Assume that Sam will be starting school in 4 years from today and that a rate of interest of 6% per year with annual compounding applies both before and during Sam's time at university