You can think of the result in any one game as being Eric's marginal free-throw percentage. Based on your previous answer, you can deduce that when Eric's marginal free-throw percentage is below the average, the average must befalling . You can now apply this analysis to production costs. For a U-shaped average total cost curve, when the marginal cost curve is below the average total cost curve, the average total cost must befalling . Also, when the marginal cost curve is above the average total cost curve, the average total cost must berising . Therefore, the marginal cost curve intersects the average total cost curveat its minimum