IMO Corporation has 3 million ordinary shares outstanding that are currently priced at $1.25 each and have a beta of 0.45. The company has 250,000 preference shares trading at $2.5 each. The return on the stock market is 5% p.a., the risk-free return is 1.5% p.a., and the company tax rate is 30%. Eight years ago IMO Corporation issued bonds with a total face value of $4 million. One bond has a face value of $100,000. The bonds have a coupon rate of 2% p.a. and coupons are paid semi-annually. The bonds mature in seven years from today. The bonds currently yield 3% p.a.

What proportion of the firm's capital structure is debt?

[Where applicable, show as much working out as possible