Problem: Addams Family Value Stores' President, Kathie Gaylord, has been reviewing her firm's financial statements. She knows that the firm's return on equity is 17.8 percent, the total debt to total asset ratio is 25 percent, and the total asset turnover is 2.52. She is sure that the firm's accountant told her the firm's net profit margin before he went home, but she can't remember. Please help her determine the firm's net profit margin.