Suppose Caterpillar, Inc., has 652 million shares outstanding with a share price of $72.03, and $24.72 billion in debt. If in three years, Caterpillar has 710 million shares outstanding trading for $86.64 per share, how much debt will Caterpillar have if it maintains a constant debt-equity ratio? The amount of debt required in three years will be $ billion. (Round to two decimal places.)