WASHINGTON — The U.S. Department of Agriculture said Sept. 30 it had bought and immediately re-sold 136,026 tons of refined beet sugar under the Feedstock Flexibility Program in continued efforts to reduce the sugar oversupply and avoid forfeitures on sugar loans that matured Sept. 30.The U.S.D.A. said it paid about $65.9 million for the sugar and sold it for about $12.6 million for a net cost of $53.3 million. A total of 415,000 tons of sugar had been offered in the F.F.P. tender, but the U.S.D.A. buys only the amount of sugar that can be immediately resold to biofuels producers. In the first F.F.P. tender a few weeks ago, the U.S.D.A. bought and resold 7,118 tons of sugar out of 99,375 tons offered.