I like to use the flat rate boxes, so I would guess approximately $7. If I split the cost with you as mentioned in the description, I would charge you $3.50
It is a bit too small for a binder. If you did put it in, I don't think it would zip. I don't have it with me this week, as it is at my house and I am away for the week for school. I can get measurements this weekend if you wish.