asking for 200 firm.
Sorry.... I can't resist...
since you are not a merchant under the UCC, Korean Moon, you can not make a "firm offer."
What you mean to say is that you are selling it for $200 and not open to negotiations - any offer less than $200 will be rejected.
A firm offer means that the goods are for sale and the offer to sale cannot be revoked by the merchant for a reasonable period of time.
Under the UCC, money talks and the first person to drop $200 on the barrel takes the AEG. If you were a merchant making a "firm offer" the buyer could sue you for breach if you failed to deliver the AEG.
But actually, you are inviting offers to purchase the AEG from the public and you can accept or reject.
Fukkin lawyers anyway...