BRB Corporation has 5 million ordinary shares outstanding that are currently priced at $4 each and have a beta of 0.8. Eight years ago the company issued bonds with a total face value of $7 million. One bond has a face value of $100,000. The bonds have a coupon rate of 4% p.a. and coupons are paid semi-annually. The bonds mature in seven years from today. The bonds currently yield 5% p.a., the return on the stock market is 8% p.a., the risk-free return is 2% p.a., and the company tax rate is 30%. The company has 600,000 preference shares trading at $5 each. What proportion of the firm's capital structure is preference shares? [Where applicable, show as much working out as possible, otherwise you may be penalised)