Issue cost

It doesn’t matter whether you include them as an outflow in the base case NPV or subtract them separately later (after the tax benefit on the debt used). The end result will be he same.

As far as how the amount is calculated, it depends on whether they are paid out of the debt raised (which means they raise more than the amount needed to the project and therefore pay more interest and get more tax relief) or are paid out of available cash. If it is not clear which from the question, then do either but, as always, state your assumption.