The Treasury sold $7 billion in three-month bills at an average discount rate of 8.36%, up from 8.15% last week. Another $7 billion was sold in six-month bills at an average rate of 8.53%, up from 8.25%. The rates were the highest since Dec. 10, 1984, when three-month bills averaged 8.38% and six-month bills 8.57%. The new discount rates understate the actual return to investors--8.66% for three-month bills and 9.04% for six-month bills. The discount rate reflects the price discount received when government securities are purchased at less than face value.