[youtalkfunny]

Be sure to write "Pay by mail" on the ticket, and sign it, or whatever they tell you to do in the instructions on the back of the ticket.

I worked in the Post Office one summer. Every piece of Registered and Certified mail is treated VERY seriously. It doesn't change hands without a signature, every step of the way.

As for the return envelope, a first-class stamp will suffice.

FYI, most books let the "Pay by mail" tickets pile up for a week or two, then process them all at once.