narrow falls lumber has total assets of $913,600, total debt of $424,500, net sales of $848,600, and net income of $94,000. the tax rate is 21 percent and the dividend payout ratio is 30 percent. what is the firm's sustainable growth rate? a) 13.97 percent b) 14.46 percent c) 15.54 percent d) 12.63 percent e) 14.91 percent