Final answer:
In the oligopoly version of the prisoner's dilemma, the rational strategy for both firms, leading to Nash equilibrium, is to increase output, resulting in lower profits compared to potential cooperation.
Step-by-step explanation:
The concept in question is related to a classic example in game theory, where firms within an oligopoly must decide whether to cooperate or to act in their own self-interest. According to the given scenario, both Firm A and Firm B will choose to expand their output because it dominates their strategy regardless of the other firm's decision. Their inability to trust each other to hold down output leads to a prisoner's dilemma, where the individually rational choice leads to a worse outcome for both firms compared to possible cooperation. Therefore, the Nash equilibria in this context are the strategies where both firms choose to expand their output.