BNY plc, which pays corporation tax at 25%, has the following capital structure:

Ordinary shares: 900,000 ordinary shares of nominal value 25p per share. The market value of the shares is 49p per share. A dividend of 7p per share has just been paid, and dividends are expected to grow by 7% per year for the foreseeable future.

Preference shares: 350,000 preference shares of nominal value 60p per share. The market value of the shares is 32p per share and the annual net dividend of 7.5% has just been paid.

Debentures: GHC100,000 of 10-year redeemable debentures with a market price of GHC92 per GHC100 block. These debentures have a coupon rate of 10% and the annual interest payment has just been made.

Calculate the weighted average after-tax cost of capital of BNY plc.