8. A firm’s long-run average total cost curve is formed by

a. points of tangency with its short-run average total cost curves.

b. points of tangency with its short-run marginal cost curves.

c. linking the intersections of its short-run marginal cost curves and its short-run average variable cost curves.

d. linking its short-run average fixed cost curves.

e. linking the minimum points of its short-run marginal cost curves.