(a) In a sale by auction if goods are put up in lots each lot is the subject of a separate sale.
(b) A sale by auction is complete when the auctioneer so announces by the fall of the hammer or in other customary manner. Where a bid is made while the hammer is falling in acceptance of a prior bid, the auctioneer has discretion to reopen the bidding or declare the goods sold under the bid on which the hammer was falling.
(c) A sale by auction is with reserve unless the goods are in explicit terms put up without reserve. In an auction with reserve, the auctioneer may withdraw the goods at any time until the auctioneer announces completion of the sale. In an auction without reserve, after the auctioneer calls for bids on an article or lot, that article or lot cannot be withdrawn unless no bid is made within a reasonable time. In either case a bidder may retract a bid until the auctioneer's announcement of completion of the sale, but a bidder's retraction does not revive any previous bid.
(d) If the auctioneer knowingly receives a bid on the seller's behalf or the seller makes or procures such a bid, and notice has not been given that liberty for the bidding is reserved, the buyer has the option to avoid the sale or take the goods at the price of the last good faith bid before the completion of the sale. This subsection does not apply to a bid at a forced sale.