Bidding box for home-played games. Use of bidding boxes has several advantages over oral bidding: it reduces noise in the room, prevents bidding being overheard at neighboring tables, allows easier review of the auction, and reduces the opportunity to pass unauthorized information to one's partner (intentionally or not) by the manner and intonation in which one makes one's bid. A bidding box is typically a plastic box with two slots, each containing a set of bidding cards. One slot contains 35 cards with symbols of bids (5 denominations—clubs (), diamonds (), hearts (), spades (), and notrump (NT)—in seven levels of bidding,
Vickrey auction make $2 instead of $0. Because the seller's revenue can go up when bids are either increased or decreased, the seller's revenues are non-monotonic with respect to bids. The dominant strategy in a Vickrey auction with a single, indivisible item is for each bidder to bid their true value of the item. Let formula_1 be bidder i's value for the item. Let formula_2 be bidder i's bid for the item. The payoff for bidder i is formula_3 The strategy of overbidding is dominated by bidding truthfully. Assume that bidder i bids formula_4. If formula_5 then the bidder would win the