Delta Corporation has the following capital structure: a. If the firm has $26 million in retained earnings, at what size capital structure will the firm run out of retained earnings? (Enter your answer in millions of dollars (e.g., $10 million should be entered as "10").) b. The 6.1 percent cost of debt referred to earlier applies only to the first $13 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? (Enter your answer in millions of dollars (e.g., $10 million should be entered as "10").)