The Treasury Department sold $6.6 billion in three-month bills at an average discount rate of 5.55%, down from 5.62% last week. Another $6.6 billion was sold in six-month bills at an average discount rate of 5.54%, down from 5.68% last week. The rates were the lowest since three-month bills sold for 5.47% on May 11 and six-month bills averaged 5.51% on March 2. The new discount rates understate the actual return to investors--5.72% for three-month bills, with a $10,000 bill selling for $9,859.70, and 5.80% for six-month bills selling for $9,719.90. The discount rate reflects the price discount received when government securities are purchased at less than face value.