CandyCo is a foreign corporation that makes taffy for sale worldwide. CandyCo markets its candy in the United States through a U$.$S$.$ subsidiary. A review of the U$.$S$.$ subsidiary's interest expense account indicates that it paid $$400,000$ of interest to an unrelated foreign corporation on debt that is unassignable, $$100,000$ of interest to a foreign corporation that owns $15\%$ of CandyCo's stock, and $$260,000$ of interest to a U$.$S$.$ corporation. Which of the following statements is true?

a$.$ CandyCo is subject to withholding on the $$100,000$ of interest paid to the foreign corporation owning $15\%$ of the stock because it does not qualify for the portfolio interest exception.

b$.$ CandyCo is subject to withholding on the $$400,000$ of interest to an unrelated foreign corporation on debt that is unassignable because it does not qualify for the portfolio interest exception.

c$.$ CandyCo is subject to withholding on the $$260,000$ of interest paid to a U$.$S$.$ Corporation because it is FDAP income.

d$.$ None of the above are true.