Interest rates on short-term Treasury bills were mixed in Tuesday's auction. Rates on three-month bills rose while six-month bills declined. The Treasury Department auctioned $15 billion in three-month bills at a discount rate of 4.780 percent, up from 4.775 percent last week. Another $14 billion in six-month bills was auctioned at a discount rate of 4.805 percent, down from 4.810 percent last week. The three-month rate was the highest since three-month bills averaged 4.785 percent a month ago. The six-month rate was the lowest since 4.735 percent two weeks ago. The discount rates reflect that the bills sell for less than face value. For a $10,000 bill, the three-month price was $9,879.17 while a six-month bill sold for $9,757.08.