Spartan Corporation, a U.S. company, manufactures green eyeshades for sale in the United States and Europe. All manufacturing activities take place in Michigan. During the current year, Spartan sold 8,400 green eyeshades to European customers at a price of $10.40 each. Each eyeshade costs $4.20 to produce.

For each independent scenario, determine the source of the gross income from sale of the green eyeshades.

a. All of Spartan's production assets are located in the United States.

b. Half of Spartan's production assets are located outside the United States.