Final answer:
The subject of this question is Economics, and it relates to the concept of market power, where a single seller has control over the price of a good or service due to limited competition.
Step-by-step explanation:
The subject of this question is Economics. In this scenario, the gas station has exclusive rights to operate along a private toll-road, allowing them to set the price of gasoline. This concept is related to the economic principle of market power, where a single seller has control over the price of a good or service due to limited competition.