Answer:
The correct answer is:
0.50 (B)
Explanation:
The Lerner index is used by monopolists to measure market/monopolist power, and it is defined as the percent markup of price over marginal cost.
It is given by the formula:
[tex]L = \frac{P - MC}{P}\\where:\\L = Lerner\ index\\P = price = \$40\\MC = marginal\ cost = \$20\\\\L = \frac{40\ -\ 20}{40} \\L = \frac{20}{40}\\ L = 0.5[/tex]
Note: in a perfectly competitive market, L = 0, which makes Price = Marginal cost in the equation above. But in a competitive market, it is always the case that L ≥ 0
