The Treasury Department sold $6.4 billion in new three-month bills at an average discount rate of 6.32%, down from 6.45% last week. Another $6.4 billion was sold in new six-month bills at an average discount rate of 6.64%, down from 6.72% last week. The rates were the lowest since Aug. 31, when three-month bills sold for 6.19% and six-month bills averaged 6.34%. The new discount rates understate the actual return to investors--6.53% for three-month bills, with a $10,000 bill selling for $9,840.20, and 6.99% for six-month bills selling for $9,664.30. The discount rate reflects the price discount received when government securities are purchased at less than face value.