Answer:
the number of people involved is small.
Step-by-step explanation:
Coase theorem was developed in 1960 by a British economist and author named Ronald Coase.
Coase theorem states that when the actions of a party (X) negatively affects or harm another party (Y), then party Y should be able to create an incentive for party X to stop or limit the action creating such harm.
Generally, when transaction cost are low, the two parties are able to bargain and reach a mutual agreement in the presence of an externality such as a pollution.
The Coase theorem will apply only if the number of people involved is small, the cost of negotiation is low and there are well defined property rights.