A company currently has the debt$-$to$-$equity ratio of $1/3.$ Its cost of debt is $6\%$ before tax and its cost of equity is $12\%.$ The tax rate is $21\%.$ What is its current weighted average cost of capital $($WACC$)?$ Assume that the company is considering raising the debt$-$to$-$equity ratio to $1/2.$ What is its new cost of equity under the new debt$-$to$-$equity ratio? What is its new weighted average cost of capital $($WACC$)$ under the new debt$-$to$-$equity ratio? Does raising the debt ratio increase firm value? Why or why not?