PROBLEM 3 Rick Rocker, a citizen and resident of country F, conducts a three-concert tour in the United States. A multi-talented individual, Rocker sells tickets to his concert from the ticket booth before his concert begins. During intermission, he sells beverages from the concession stand. Afterwards, Rocker sells t-shirts at the concession stand. Is Rocker engaged in a U.S. trade or business? Explain. If Rocker is engaged in a U.S. trade or business, what income is subject to U.S. tax? When does Rocker pay any U.S. tax?