Donald is the sole shareholder of Donald Corporation. The week before the corporation files for bankruptcy, Donald paid back a loan to his father that he used to help start the business last year. Although the loan was not due for another year, Donald paid off the balance entirely. Which of the following is true?

a. Paying back the loan was a preferential transfer.

b. Paying back the loan was a portable transfer.

c. Paying back the loan was in the ordinary course of business.

d. Both A and B are correct.