WASHINGTON (AP) — Interest rates on short-term Treasury bills were mixed in Tuesday’s auction with rates on three-month bills rising to their highest level in six weeks, while rates on six-month bills were unchanged.

The Treasury Department auctioned $25 billion in three-month bills at a discount rate of 0.030 percent, up from 0.025 percent last week. Another $23 billion in six-month bills was auctioned at a discount rate of 0.050 percent, unchanged from last week.

The three-month rate was the highest since these bills averaged 0.035 percent six weeks ago on April 14.

The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,999.24, while a six-month bill sold for $9,997.46. That would equal an annualized rate of 0.030 percent for the three-month bills and 0.051 percent for the six-month bills.

Separately, the Federal Reserve said Tuesday that the average yield for one-year Treasury bills, a popular index for making changes in adjustable rate mortgages, was 0.09 percent last week, unchanged from the previous week.

Treasury’s regular Monday auction for three-month and six-month bills was held on Tuesday this week because of the Memorial Day holiday.

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