What are the conclusions about the cost of production and efficiency in the long-run equilibrium of a perfectly competitive industry?

Three conclusions regarding the cost of production and efficiency into the long-run equilibrium of a perfectly competitive industry as follows:

a. Within a perfectly competitive industry into equilibrium, the value of marginal cost is similar for all firms.

b. In a perfectly competitive industry along with free entry and exit, every firm will have zero economic profits into long- run equilibrium.

c. The long-run market equilibrium of a perfectly competitive industry is effective: no equally beneficial transactions go unexploited.