Answer:
monopoly, but self-interest often drives them closer to the perfectly competitive outcome.
Explanation:
In the given situation, the oligopoly tried to act like the monopoly via collusion but at the same time they would tend to cheat that drives the profit and the price per unit is less also it acted as the competitive firm
so here the self-interest would also be drives them near to the perfectly competitive result
hence, the above represent the answer