Number of payments.$$Your grandfather will sell you a piece of beachfront property for $$$$67,500.$ He says the price is firm whenever you can pay him cash. You know your finances will only allow you to save $$$$6,400$ a year and you can make $7\%$ on your investment. If you invest faithfully every year at the end of the$$ year, how long will it take for you to accumulate the necessary $$$$67,500$ future cash for the beachfront$$ property?