Ten years ago, Godsway Ltd issued GH2.5 million of 6% discounted debenture at GH98 per GH100 nominal. The debentures are redeemable in 6 years from now at a GH2 premium over nominal value. They are currently quoted at GH79 per debenture, ex interest. The company pays tax at the rate of 30%. Required: Estimate the after tax cost of the debenture.