Impact of financing on Investment decisions and adjusted present value

I just did a question in the study text on the topic above but i am struggling with the Market Value of the debenture. I am not sure how they got that answer and I cant seem to figure it out. Here is the question:

Nile Inc is considering an investment of capital to be raised from the issue of new ordinary shares and debentures in a mix which will hold its gearing ratio approximately constant. It wishes to estimate its weighted average cost of capital.

The company has an issued share capital of 1m ordinary shares of $1 each; it has also issued $800,000 of 8% Debentures. The market price of ordinary shares is $4.76 per share and debentures are priced at $77 per cent. Dividends and interest are payable annually. An ordinary dividend has just been paid; the next installment of interest is payable in the future. Debentures are redeemable at par in 15 years’ time.

A summary of the most recent statement of financial position runs as follows.

Ordinary share capital $1,000,000
Reserves $1,553,000
Deferred taxation $ 164,000
Debentures $ 800,000

Total $3,517,000

Assume that there have been no changes in the system or rates of taxation during the last five years, that the rate of corporate tax is 35% and that the standard rate of income tax is 30%.

Required – Calculated Nile’s Inc’c weighted average cost of capital.

I have calculated the cost of equity correctly and also the market value of equity.
The answer they got for the market value of debentures is $552,000. I also calculated correctly the cost of debenture but i can’t seem to get that answer that they got please help me