Buyer mailed a signed order to Seller that read: "Please ship us 10,000 widgets at your current price." Seller received the order on January 7 and that same day mailed to Buyer a properly stamped, addressed, and signed letter stating that the order was accepted at Seller's current price of $10 per widget. On January 8, before receipt of Seller's letter, Buyer telephoned Seller and said, "I hereby revoke my order." Seller protested to no avail. Buyer received Seller's letter on January 9. Because of Buyer's January 8 telephone message, Seller never shipped the goods. Under the relevant and prevailing rules, is there a contract between Buyer and Seller as of January 10? 
No, because the order was an offer that could be accepted only by shipping the goods; and the offer was effectively revoked before shipment.  No, because Buyer never effectively agreed to the $10 price term.  Yes, because the order was, for a reasonable time, an irrevocable offer.  Yes, because the order was an offer that seller effectively accepted before Buyer attempted to revoke it.