I will check at the post office. Media Mail is usually the cheapest way to mail books, but it is the slowest so I will check a few different ways today.
I just looked it up. The book weighs 8 ounces. The flat rate priority box is 5.20. It looks like it would fit in it. For First Class mail is it 2.75. The online estimate doesn't show Media Mail so I would guess (and would charge) 1.75 for it. You get to choose the method. Winne bidder just needs to let me know and pay through Paypal.