Metro Inns has total assets of $$800$ m$,$ total debt of $$200$ m$,$ net sales of $$800$ m$,$ and net income of $$100$ m$.$ The tax rate is $21$ percent, and the dividend payout ratio is $30$ percent. Assume the firm$$s spontaneous liabilities are ignorable. What is the firm's sustainable growth rate?

$7\mathrm{.}12\%$

$9\mathrm{.}59\%$

$12\mathrm{.}53\%$

$13\mathrm{.}21\%$

$15\mathrm{.}23\%$