Assume that a firm's value of equity is $$50$ million, and it has $$40$ million of permanent debt. The firm pays $5\%$ interest on its debt and its corporate tax rate is $25\%.$ What is the firm's present of value of the interest tax shields?

Question $1$ options:

$$9$ million

$$10$ million

$$15\mathrm{.}75$ million

$$18$ million

None of the above