Problem 11-27 (Static) Marginal cost of capital [LO11-5] Delta Corporation has the following capital structure: a. If the firm has $18 million in retained earnings, at what size capital structure will the firm run out of retained earnings? Note: Enter your answer in millions of dollars (e.g., \$10 million should be entered as "10"). b. The 8.1 percent cost of debt referred to earlier applies only to the first $14 million of debt. After that the cost of debt will go up. At what size capital structure will there be a change in the cost of debt? Note: Enter your answer in millions of dollars (e.g., $10 million should be entered as "10")