On November 23, Blackburn, a dress manufacturer, mailed to Conroy a written and signed offer to sell one thousand sundresses at $50 per dress. The offer stated that it would "remain open for ten days" and that it could "not be withdrawn prior to that date." Two days later, Blackburn, noting a sudden increase in the price of sundresses, changed his mind. Blackburn therefore sent Conroy a letter revoking the offer. The letter was sent on November 25 and received by Conroy on November 28. Conroy chose to disregard the letter of November 25; instead, she happily continued to watch the price of sundresses rise. On December 1, Conroy sent a letter accepting the original offer. The letter, however, was not received by Blackburn until December 9, due to a delay in the mail. Conroy has demanded delivery of the goods according to the terms of the offer of November 23, but Blackburn has refused. Does a contract exist between Conroy and Blackburn? Explain.