Airbnb has a cost of equity of 10.99 percent, a pretax cost of debt of 5.44 percent, and a tax rate of 39 percent. The company's capital structure consists of 71 percent debt on a book value basis, but debt is 37 percent of the company's value on a market value basis. What is the company's WACC? O a. 7.51% O b.8.94% O c. 12.31% O d. 9.53% O e. 8.15%