Back in April, Billy Ackman put his UWS co-op at the Majestic on the market for $10 million, after his mother-in-law convinced him it wasn't worth the $12 million he wanted. Curbed reports Ack-boy has sold the pad, and is headed up the block to the Beresford at 211 Central Park West. Due to building rules, Ackman is not allowed to keep his "guest" apartment when he goes, so he's putting the place-- which he bought for $450,000 in 2007 and then put $250,000 into renovating-- up for sale, and asking for $950,000. If somebody doesn't buy this thing-- and everything inside, including flat screens and that little Target dog, which Bill has grown seriously fond of--, ASAP, Ackman is auctioning it off December 8th. Ackman has told residents he'll be the auctioneer (and has been practicing getting the voice just right with a friend), and will be providing "some excellent wines for participants" in case anyone's looking for free drinks.