discuss this for American Airlines Inc. thank you !

The Weighted Average Cost of Capital (WACC): It is very important that you obtain your final estimate of your WACC based on the market value weights of debt, preferred stock and equity of your firm. If the market value of your debt is unavailable, it is acceptable to use the book value of debt as shown on your balance sheet. 5. Once you obtain your final WACC estimate, provide brief commentary on your view of your estimate, and whether it provides an appropriate reflection of the risk of your firm as you see it. Keep in mind that the risk of the overall market (the S&P 500), represents an average annual return of about 11%