If all of the firms in an oligopoly successfully collude and form a cartel, then total profit for the cartel is equal to what it would be if the market were a monopoly.

Collude

To engage in a secret agreement or cooperation, especially with the intention of cheating or deceiving others.

Cartel

An association of independent businesses or countries that work together to control production, pricing, and marketing of goods to monopolize a market.

Monopoly

A firm that is the sole seller of a product without any close substitutes.