I'm putting a 9x12 SASE and a letter in a #10 envelope (10.4x24.1 cm).
So how many stamps would I put on the #10 envelope?
I've already gone to the post office before, and the lady said a 42 cent stamp was fine for the outside envelope, but that day was kind of a rushing day and she just said anything...unless, of course, she's right!

Any help would be greatly appreciated!!