Interest rates on short-term Treasury bills rose in Monday’s auction with rates on three-month bills rising to the highest level in a year. The Treasury Department auctioned $33 billion in three-month bills at a discount rate of 0.115 percent, up from 0.085 percent last week. Another $31 billion in six-month bills was auctioned at a discount rate of 0.145 percent, up from 0.125 percent last week. The three-month rate was the highest since these bills averaged 0.145 percent on Feb. 28, 2011. The six-month rate was the highest since six-month bills averaged 0.150 percent on Aug. 1 of last year.