The following information relates to AAL Corporation (AAL) : AAL has 5 million ordinary shares outstanding. The company has 600,000 preference shares trading at $4 each. Ten years ago the company issued bonds with a total face value of $8 million. One bond has a face value of $100,000. The bonds have a coupon rate of 5% p.a. and coupons are paid annually. The bonds mature eight years from today. The ordinary shares are currently priced at $5 each. AAL has a beta of 1.8. Also, the market yield on the AAL preference shares is 8%. The bonds currently yield 6% p.a. The return on the stock market is 9% p.a. The risk-free return is 4.5% p.a. The company tax rate is 30%. What proportion of the firm's capital structure is debt? [You must show your working out, otherwise, you will be penalised]