WASHINGTON (AP) — Interest rates on short-term Treasury bills were mixed in Monday's auction with rates on three-month bills climbing to their highest level in more than eight years while rates on six-month bills declined.

The Treasury Department auctioned $39 billion in three-month bills at a discount rate of 1.050 percent, up from 1.040 percent last week. Another $33 billion in six-month bills was auctioned at a discount rate of 1.105 percent, down from 1.125 percent last week.

The three-month rate was the highest since these bills averaged 1.250 percent on Oct. 20, 2008. The six-month rate was the lowest since these bills averaged 1.100 percent five weeks ago on June. 12.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,973.46 while a six-month bill sold for $9,944.14. That would equal an annualized rate of 1.067 percent for the three-month bills and 1.127 percent for the six-month bills.

Separately, the Federal Reserve said Monday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, stood at 1.22 percent last Friday, little changed from 1.23 percent at the start of the week on July 10.