text: In the U.K., participants in this situation are subject to the RPI-X rule.
full_question: In the U.K., participants in this situation are subject to the RPI-X rule. Values approaching one for the Lerner index characterize this situation. The Coase conjecture predicts the price in this situation across an infinite time horizon. The "natural" form of this situation is characterized by high barriers to entry and by economies of scale. In this situation, the quantity is determined by taking the marginal revenue equal to marginal cost, leading to a higher profit and price than in perfect competition. For 10 points, name this situation in which one company is the sole provider of a commodity.
first_sentence: In the U.K., participants in this situation are subject to the RPI-X rule.