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    HL

    Monopolistic Competition – Long-Run Equilibrium (Normal Profit)

    Microeconomics

    A diagram illustrating a firm in monopolistic competition in long-run equilibrium, where it earns normal profit. The ATC curve is tangent to the demand curve (AR), meaning total revenue equals total cost.

    Diagram & Curves
    Monopolistic Competition – Long-Run Equilibrium (Normal Profit)

    Curves and Elements

    ar

    AR = D: The average revenue or demand curve, downward sloping due to product differentiation.

    mr

    MR: Marginal Revenue, lies below AR because the firm must lower price to sell more.

    mc

    MC: Marginal Cost, intersects MR at the profit-maximizing output Qm.

    atc

    ATC: Average Total Cost, tangent to AR at Qm, indicating zero economic profit.

    q

    Qm: The output level where MR = MC.

    p

    Pm: The price corresponding to Qm on the AR curve.

    Key Explanations
    1

    Firms in monopolistic competition face a downward-sloping demand curve (AR = D) due to product differentiation.

    2

    The profit-maximizing quantity is found where marginal cost (MC) equals marginal revenue (MR).

    3

    The corresponding price (Pm) is determined by extending a line from Qm up to the AR curve.

    4

    In the long run, the ATC curve is tangent to the AR curve at Qm, indicating that the firm earns normal profit (no economic profit).

    5

    This outcome results from the entry of new firms eroding any abnormal profits that existed in the short run.

    Example Exam Question
    Using a diagram, explain why a firm in monopolistic competition earns only normal profit in the long run.

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