An investor trading in bonds is looking for 4% return on his purchases. He buys bonds with a few years left before maturity holds them, and redeems them for face when they mature. Looking through the bond listing, he finds a bond listed with a face that pays 3% interest face value each year, and is priced at exist1, 747. How many years (at most) must be left before maturity on this bond in order to meet the investor's desired percent return?