Participants in a market, buyers and sellers, may need the service of an intermediary who will put them into contact and give them information about their potential trading partner. The intermediary chooses what price it will charge to each side to have access to its service. It also chooses...

Quite often, a firm has to decide between investing in a safe project (``small'') where rewards and losses remain moderate and a risky alternative (``big'') where the rewards and the losses are larger. We study such a choice in a context where the probability of success depends both on the...