NatNah, a builder of acoustic$$ accessories, has no debt and an equity cost of capital of $15\%.$ Suppose NatNah decides to increase its leverage to maintain a market$$ debt$-$to$-$value ratio of $0\mathrm{.}2.$ Suppose its debt cost of capital is $9\%$ and its corporate tax rate is $23\%.$ If$$ NatNah's pre$-$tax WACC remains$$ constant, what will be its$($effective after$-$tax$)$ WACC with the increase in$$ leverage?

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Part $1$

The effective$$ after$-$tax WACC will be

$$

enter your response here$\%.($Round to two decimal$$ places.$)$