Delta Corporation has the following capital structure: a. If the firm has S36 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., exist10 million should be entered as "10").) Capital structure size (X) million b. The 7.2 percent cost of debt referred to earlier applies only to the first exist12 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., exist10 million should be entered as "10").) Capital structure size (Z) million