The Treasury Department sold $8 billion in new three-month bills at an average discount rate of 5.41%, up from 5.23% last week. Another $8 billion was sold in new six-month bills at an average discount rate of 5.54%, up from 5.30% last week. The rates were the highest since three-month bills sold for 5.64% and six-month bills averaged 5.65% last Aug. 18. The new discount rates understate the actual return to investors--5.56% for three-month bills with a $10,000 bill selling for $9,863.20 and 5.78% 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.