Does acceptance of an offer constitute a legal contract?

I assume from this scenario that you were supposed to be the buyer, and that after you accepted the seller's offer, the seller breached your contract by selling the product to someone else.  You can sue the seller for the lesser of (a) the difference between you agreed to pay and the value of the goods (evidence of which is the price the seller received from the other buyer) or (b) you can buy replacement goods on the open market and sue the seller for the difference between what you paid and what you had contracted to pay the seller.