During the latest year Ruth Corp. had sales of $300,000 and a net income of $20,000, and its year-end assets were $200,000. The firm's total debt to total assets ratio was 40%. Based on the Du Pont equation, what was the firm's ROE?
A. 15.33%
B. 15.67%
C. 16.00%
D. 16.33%
E. 16.67%