You have just won the Publisher's Clearinghouse lottery of $$50,000$ per year for twenty years with the first payment one year later followed by nineteen more end$-$of$-$the$-$year cash flows. As an alternative, you are offered a lumpsum lottery payment of $$679516\mathrm{.}3172$ today. What is the interest rate such that you will be indifferent between the two options? $($I know it's $4$ but I need help with working it out$)$