The Treasury sold $7.6 billion in new three-month bills at an average discount rate of 5.72%, down from 5.78% last week. Another $7.6 billion was sold in new six-month bills at an average discount rate of 5.77%, down from 5.80% last week. The rates for three-month bills were the lowest since September, 1977, when they averaged 5.55%. Rates for six-month bills were the lowest since they sold for 5.68% in August, 1977. The new discount rates understate the actual return to investors--5.88% for three-month bills and 6.03% for six-month bills. The discount rate reflects the discount received when government securities are purchased at less than face value.