Short-Term T-Bill Rates Fall: The Treasury Department sold $11.1 billion in three-month bills at an average discount rate of 5.17%, down from 5.19% last week. An additional $11.2 billion was sold in six-month bills at an average rate of 5.30%, down from 5.38%. The three-month bill rate is the lowest since they sold for 5.07% on Aug. 26. The six-month bill rate is the lowest since they averaged 5.16%, also on Aug. 26. The discount rates understate the actual return to investors: 5.31% for three-month bills, with a $10,000 bill selling for $9,869.30, and 5.52% for a six-month bill selling for $9,732.10. In a separate report, the Federal Reserve Board said the average yield for one-year Treasury bills, the most popular index for making changes in adjustable-rate mortgages, rose to 5.95% last week from 5.81% the previous week.