Cost of debt??? current, before, issue, right

dvilayphet

When calculating WACC, which one do you take as before tax cost of debt:

1/ YTM of firm's long-term debt
2/ Coupon rate on firm's current long-term debt
3/ YTM of firm's short-term debt
4/ Coupon rate on firm's current short-term debt
5/ Expected YTM of bond if firm is to issue more bond

That's all I can think of right now. Is there a priority principle for this thing?