Allison Engines Corporation has established a target capital structure of $40$ percent debt and $60$ percent common equity. The current market price of the firm's stock is PO $=$$$35\mathrm{.}1$; its last dividend was $DO=$$$3\mathrm{.}1,$ and its expected dividend growth rate is $5\mathrm{.}7$ percent. What will Allison's marginal cost of retained earnings, rs$,$ be$?$

$16\mathrm{.}04\%$

$15\mathrm{.}54\%$

$17\mathrm{.}04\%$

$16\mathrm{.}54\%$

$15\mathrm{.}04\%$