what is the amount of stamps i should put on a 13x10 envelope? (I can't by any more 9x12's until at least four days)
and how many IRC's should I include on a 9x12 to Austrlia or the UK? I tried to read the thread about this but got very confused

I'm from the US. What's the cost per IRC?
THANK YOU! VERY VERY MUCH!