How many IRC's Will i need Australia ? Read

[leonel9]

So i live in Australia NSW and i am going to send a letter to Selena Gomez when she is preforming at the new york state fair but i don't know how many to use how much is 1 irc worth in american dollars i heard irc's cost $3.60 here in oz but will i need 2 or is one fine i am pretty sure my photo weighs less then 50 grams but will weigh less due too the sae really need help on this thanks