Banana Corporation has 4 million ordinary shares outstanding that are currently priced at $8.50 each and have a beta of 1.4. The company has 750,000 preference shares trading at $6 each. Eight years ago the company issued bonds with a total face value of $5 million. One bond has a face value of $250,000. The bonds have a coupon rate of 4% p.a. and coupons are paid annually. The bonds mature in six years from today. The bonds currently yield 2.5% p.a., the return on the stock market is 8% p.a., the risk-free return is 2.5% p.a., and the company tax rate is 30%.

What proportion of the firm's capital structure is preference shares?