Explain the cost advantage of a firm operating at constant returns to scale

If we compare a firm operating in the constant returns to scale range to a firm that is operating in the economies of scale range, there are significant differences. The firm in the economies of scale range has not yet reached the lowest possible cost per unit because it is producing too small of a quantity. In contrast, the firm in the constant cost range is producing beyond its minimum efficient scale, with the lowest possible cost per unit and therefore enjoys an advantage over smaller firms with higher costs.