T-Bill Rates Plunge: The Treasury sold $6.4 billion of new three-month bills at an average discount rate of 8.07%, down from 8.22% last week. Another $6.4 billion of new six-month bills was sold at an average discount rate of 7.78%, down from 8.08% last week. The rates were the lowest since three-month bills sold for 7.98% last Dec. 12 and six-month bills averaged 7.71% last Nov. 7. The discount rates understate the actual return to investors--8.35% for three-month bills, with a $10,000 bill selling for $9,796.00, and 8.21% for a six-month bill selling for $9,606.70. The discount rate reflects the price discount received when government securities are purchased at less than face value.