From the following list, select all the statements that apply to the average cost curve.

a. The curve is saucer-shaped.
b. At any output, the height of the curve is the sum of the heights of the average variable cost and average fixed costs curves.
c. The curve reaches a minimum where it intersects the marginal cost curve.
d. The curve is negatively sloped throughout its entire range, becoming flatter at higher output levels.