Spartan Corporation, a U.S. company, manufactures widgets for sale in the United States and Europe. All manufacturing activities take place in the United States. During the current year, Spartan sold 100,000 widgets to European customers at a price of $5 each. Each widget costs $2 to produce. All of Spartan's production assets are located in the United States. Spartan ships its widgets FOB, place of destination. What amount of Spartan's gross profit is treated as coming from foreign sources? Explain