A real estate development company is considering building a new office building in downtown. Above 20,000 square feet, the company’s managers believe they can generate approximately $600,000 in additional lease payments for every additional 1,000 square feet built. This $600,000 represents

    a. Long-run economic profit

    b. Long-run marginal revenue

    c. Long-run marginal cost

    d. Long-run average additional revenue