If the short-run cost curve of a firm is U-shaped, the marginal and average cost are equal where the

When the short-run cost curve of a firm is U-shaped, it means that initially the marginal cost of production falls, then reaches a minimum and eventually rises. The point where the marginal cost curve intersects the average cost curve is the minimum point of the average cost curve. At this point, the average cost is at its minimum value. Therefore, the answer is: where the average cost is minimum.