FED BUYS 500 MLN DLRS OF BILLS FOR CUSTOMER The Federal Reserve purchased about 500 mln dlrs of U.S. Treasury bills for a customer, a spokeswoman said. She said that the Fed bought bills maturing in June and July, and on August 27 and September 10 for regular delivery tomorrow. Dealers said that Federal funds were trading at 6-1/8 pct when the Fed announced the operation.