MARK B. FISHER, an independent trader, is the founder of MBF Clearing Corp., the largest clearing firm on the NYMEX. Fisher has taught his trading methodology, which he calls the ACD system, to more than 5,000 people, including many traders at leading hedge funds such as Tudor Investments. Fisher also runs a summer internship program at the New York Mercantile Exchange, which is open to apprentice traders and college students from a variety of backgrounds. Fisher has been trading since he was twenty-one, when he became the youngest trader ever in the silver futures pit. A 1982 summa cum laude graduate from the Wharton School of Business, University of Pennsylvania, Fisher also received his master's degree in finance and accounting from Wharton.