Question: SkyHigh Airlines has five possible investment projects for the coming year. Each project is indivisible. They are:
Project A: $5 million investment / IRR: 22%
Project B: $12 million investment / IRR: 16%
Project C: $6 million investment / IRR: 18%
Project D: $2 million investment / IRR: 14%
Project E: $3 million investment / IRR: 12%
SkyHigh's weighted marginal cost of capital schedule is 10 percent for up to $6 million of investment; 14 percent for between $6 million and $23 million of investment; and above $23 million the weighted cost of capital is 16 percent. The optimal capital budget is ________.