Imagine that 3 bidders want to buy a good in an open-bid auction. The 3 bidders come secretly together (they form a so-called bidding ring) and...

Imagine that 3 bidders want to buy a good in an open-bid auction. The 3 bidders come secretly together (they form a so-called bidding ring) and discuss their positions. They find out each other's values. Suppose the A's value is 12, B's value is 10 and C's value is 5. For simplicity, assume that only integer bids are allowed in the auction.