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

The Treasury Department sold $7.4 billion in new three-month bills at an average discount rate of 7.05%, up from 7.04% last week. Another $7.4 billion was sold in new six-month bills at an average discount rate of 7.11%, up from 7.07% last week. The rates were the highest since Dec. 2, when three-month bills sold for 7.19% and six-month bills averaged 7.26%. The new discount rates understate the actual return to investors--7.28% for three-month bills and 7.48% for six-month bills. The discount rate reflects the price discount received when government securities are purchased at less than face value.