WASHINGTON (AP) — Interest rates on short-term Treasury bills were mixed in Monday's auction, with rates on six-month bills holding steady while rates on three-month bills dipped to their lowest level in five weeks.

The Treasury Department auctioned $34 billion in three-month bills at a discount rate of 0.515 percent, down from 0.535 percent last week. Another $28 billion in six-month bills was auctioned at a discount rate of 0.670 percent, unchanged from last week.

The three-month rate was the lowest since those bills averaged 0.505 percent five weeks ago on Jan. 23.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,986.98, while a six-month bill sold for $9,966.13. That would equal an annualized rate of 0.523 percent for the three-month bills and 0.682 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, edged down to 0.80 percent on Friday, slightly below the 0.83 percent average seen on Feb. 21.