Barton Industries expects that its target capital structure for raising funds in the future for its capital budget will consist of $40\%$ debt, $5\%$ preferred stock, and $55\%$ common equity. Note that the firm's marginal tax rate is $25\%.$ Assume that the firm's cost of debt, rd$,$ is $8\mathrm{.}9\%,$ the firm's cost of preferred stock, rp$,$ is $8\mathrm{.}1\%$ and the firm's cost of equity is $11\mathrm{.}5\%$ for old equity, rs$,$ and $12\mathrm{.}1\%$ for new equity, re$.$ What is the firm's weighted average cost of capital $($WACC$1)$ if it uses retained earnings as its source of common equity? Do not round intermediate calculations. Round your answer to two decimal places.