Martha has $100 in a savings account. every month, she deposits $250 into her savings account. she sees an advertisement for a new refrigerator that’s available for $1,200. she calls the store and talks to a salesperson, who says she can purchase the refrigerator interest free by paying $80 per month until the balance of the purchase is paid. at the end of months, she still has owes $720 for the refrigerator.