Answer:
Market failure.
Explanation:
In this scenario, the port became so congested such that ships now have to wait hours queing every day just to dock. The mayor of New Monopoly realizes that the congestion at the port costs the shipping companies and his town money. This is an example of market failure.
A market failure can be defined as a situation in which the market fails to produce an efficient level of productivity or output that is required to meet demand.
This ultimately implies that, a market failure arises when there is inefficiency in the distribution or allocation of goods and services in a free market. Thus, the demand of the consumer of these goods and services are not being met with the level of supply (output) required i.e the forces of demand and supply are not efficient in producing the level of output required by the economy.
Some of the causes of market failure are imperfect information, monopoly, oligopoly, externalities etc.
