Between 1971 and 2006, the United States from time to time imposed quotas or other restrictions on importing steel. A quota says that no more than Q̅ > 0 units of steel can be imported into the country. Suppose both the domestic supply curve of steel, Sd, and the foreign supply curve of steel for sale in the United States, Sf, are upward-sloping straight lines. How did a quota set by the United States on foreign steel imports of Q̅ affect the total American supply curve for steel (domestic and foreign supply combined)?