International Taxation Question (Please answer all three parts of the question. Thank you. I appreciate it)

Problem 2

USAco is a domestic corporation that manufactures products in the U.S. for distribution in the U.S. and abroad. During the current year, USAco derives a pre-tax profit of $10 million, which includes $1 million of foreign-source income derived from a branch sales office in country X. The country X corporate income tax rate is 30% and the U.S. tax rate is 21%.

a. What would be the worldwide effective tax rate on the $1 million of foreign profits, assuming the U.S. taxes the worldwide income of domestic corporations, but allows an unlimited credit for foreign income taxes?

b. What would be the worldwide effective tax rate on the $1 million of foreign profits, assuming the U.S. allows a credit for foreign income taxes, but the credit is limited to the U.S. tax attributable to foreign-source income?

c. Would your answer to part (b) change if the foreign tax rate was 15% rather than 30%?