why would it be inefficient to exclude people from using a f

why would it be inefficient to exclude people from using a facility that had excess capacity?

Solution

A facility with excess capacity can be used to increase revenue, since additional usage does not incur additional cost (which is a normal assumption). Therefore, while a facility with excess capacity can generate additional revenue if people are allowed to use it, excluding people from usage of such facility results in loss revenue, which is the opportunity cost of exclusion.

Therefore, such exclusion results in a positive opportunity cost which lowers social efficiency and leads to inefficiency by way of deadweight loss.