Question: On December 1, Seller sent Buyer an offer to sell 5,000 widgets to Buyer for $25 apiece. The offer stated: "The offer will remain open until December 31." On December 10, Buyer answered: "The price is too high; I don't accept your offer." Then, on December 15, Buyer changed his mind and sent a telegram stating: "I accept your December 1 offer after all." Seller replied: "Your acceptance is too late, since you already rejected the offer." In turn, Buyer answered: "The acceptance is good, you promised to keep your offer open until December 31." Is there a contract under the CISG?