In a combinatorial exchange, both buyers and sellers can submit combinatorial bids. Bids are like in the combinatorial auction (that is you either accept the entire bid or you reject the entire bid), except that their values can be negative, as can the prices, representing selling instead of buying. Note that a single bid can be buying some items while selling other items. You are the exchange operator. Your objective is to maximize the surplus generated by matching profitable trades. Note that after clearing trades, you can end up with leftover inventory on your balance sheet. We assume that there is no cost/benefit in having leftover end-of-day inventory, but you cannot fall short