On January 5 AA Crystal an importer of fine glass ware conveyed to Chester a letter offering to sell 100 imported crystal wine glasses for $170 per glass. The letter indicated that the offer would remain in effect for 20 days. On January 9 there was an unexpected increase in the price of crystal glassware and AA Crystal sent a letter to Chester formally withdrawing the offer to sell. Chester received the revocation of the offer on January 11. On January 21 Chester mailed a letter accepting to the original offer to sell to him 100 imported glasses. The letter was received by the seller on January 27. Please explain whether a valid sale took place in this case or not.