The rise in interest rates on short-term Treasury securities in Monday's auction reversed a decline of the previous week. The Treasury Department sold $7.8 billion in new three-month bills at an average discount rate of 5.25%, up from 5.16% last week. Another $7.8 billion was sold in new six-month bills at an average discount rate of 5.39%, up from 5.34% last week. The rates were the highest since three-month bills sold for 5.32% on Aug. 25 and six-month bills averaged 5.65% on Aug. 18. The discount rate reflects the price discount received when government securities are purchased at less than face value.