Final answer:
In an oligopoly, sellers can increase their profits by acting like a cartel and reducing output and raising prices. However, maintaining collusion is challenging due to individual incentives and legal restrictions.
Step-by-step explanation:
In an oligopoly, a group of sellers that can restrict entry into a market can often enlarge their total profit by acting as a cartel and acting like a monopolist. This means reducing output and raising prices in order to maximize profit. However, collusion among members of the oligopoly is often difficult to maintain because each member can benefit individually from expanding output. Explicit collusion, which is when there is an explicit agreement among sellers to restrict competition, is also illegal.