Interest rates on short-term T-bills rose slightly.

The Treasury Department sold $7 billion in new three-month bills at an average discount rate of 7.18%, up from 6.99% last week. Another $7 billion was sold in new six-month bills at an average discount rate of 7.23%, up from 7.06% last week. The rates were the highest since Jan. 13, when three-month bills sold for 7.23% and six-month bills averaged 7.28%. The new discount rates understate the actual return to investors--7.41% on a $10,000 three-month bill selling for $9,818.50 and 7.61% for a six-month bill selling for $9,634.50. The discount rate reflects the price discount received when government securities are purchased at less than face value.