When a Firm Is at Its Efficient Scale of Operation

When a firm is at its efficient scale of operation it produces the

A) maximum rate of output at which long-run average cost is at a minimum.
B) minimum rate of output at which long-run average cost is at a minimum.
C) maximum rate of output where we have lowest long-run marginal cost.
D) minimum rate of output where we have lowest long-run marginal cost.
E) minimum rate of output where we have highest long-run marginal cost.