What is the triple equality that we find in pure competition after all long-run adjustments have been made?

In a constant-cost or increasing-cost industry, in the long run, P = minimum ATC = MC. The final long-run equilibrium positions of all firms have these same basic efficiency characteristics. Price (and marginal revenue)will settle where it is equal to minimum average total cost. Because the MC curve intersects the ATC curve at its minimum point, marginal cost and average total cost are equal. In long-run equilibrium, each firm produces at the output level that is associated with this triple equality.