Determine the source (U.S. or foreign) of the following items of income.
a. Interest income paid by a foreign corporation.
b. Dividend income paid by a U.S. corporation that has no foreign operations.
c. Dividend income paid by a foreign corporation that has U.S. operations that historically produce 32% of the corporation’s income.
d. Income from providing consulting services to clients with 27% of the services provided to clients on-site in Mexico.