NEW YORK (AP) - Selling: a 20-carat diamond engagement ring. Slightly used. Goes to highest bidder. That might be what the listing would sound like on eBay. But NBA player Kris Humphries is taking a slightly higher road in auctioning off the last remaining piece of his 72-day marriage to Kim Kardashian. US Weekly and other reports say Humphries is selling the ring at Christie's auction house in New York next month. The couple was officially divorced three months ago, though they split up nearly two years ago.