A mother eared $15000.00 from royalties on her cookbook. She set aside 20% of this for a down payment on a new home. The balance will be used for her son's future education. She invests a portion of the money in a bank certificate of deposit (CD account) that earns 4% and the remainder in a savings bond that earns 7%. If
the total interest earned after one year is $720.00, how much money was invested at each rate?