The following information relates to OMG Corporation. Eight years ago the company issued bonds with a total face value of $$7\mathrm{.}5$ million. One bond has a face value of $$500,000.$ The bonds have a coupon rate of $6\%$ p$.$a$.$ and coupons are paid annually. The bonds mature in six years from today. OMG Corporation has $6$ million ordinary shares outstanding that are currently priced at $$12$ each and have a beta of $0\mathrm{.}90.$ The bonds currently yield $4\%$ p$.$a$.,$ the return on the stock market is $12\%$ p$.$a$.,$ the risk$-$free return is $1\mathrm{.}5\%$ p$.$a$.,$ and the company tax rate is $30\%.$ The company has $1,250,000$ preference shares trading at $$9$ each.

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