Dec 2011, Close Co

Hi,

I am having problem in part c where it says to calculate and we have to find the makrket value of the bond:

8% Bonds ($100 nominal) 120

Financial analysts have forecast that the dividends of Close Co will grow in the future at a rate of 4% per year. This
is slightly less than the forecast growth rate of the profit after tax (earnings) of the company, which is 5% per year.
The finance director of Close Co thinks that, considering the risk associated with expected earnings growth, an
earnings yield of 11% per year can be used for valuation purposes.
Close Co has a cost of equity of 10% per year and a before-tax cost of debt of 7% per year. The 8% bonds will be
redeemed at nominal value in six years’ time. Close Co pays tax at an annual rate of 30% per year and the ex-dividend
share price of the company is $8·50 per share.

I got how the principal amount but I dont know why I am unable to find the interest part..

anybody?