18. Assume Bismuth Electronics has a book value of $6 billion of equity and a face value of $19.7 billion of debt. The market values of equity and debt are $2.5 billion and $18.5 billion. A Wall Street financial analyst determines values of equity and debt as $3 billion and $20 billion. Which of the following values should be used for calculating the firm's WACC? a. $6 billion of equity and $19.7 billion of debt b. $2.5 billion of equity and $20 billion of debt c. $3 billion of equity and $20 billion of debt d. $2.5 billion of equity and $18.5 billion of debt