Variable costs refer to the costs of that can easily be increased or decreased in a period. Select the correct answer below: outputs, long O outputs, short O inputs, long O inputs, shortIn perfect competition, a firm's long-run profits are zero when: Select the correct answer below: price intersects marginal cost below the average total cost curve price intersects marginal cost at a level equal to the average total cost O price intersects marginal cost above the average total cost curve price does not intersect marginal cost7- 6 Price ($) Demand 2- 10 20 30 40 50 60 70 80 90 100 Quantity (Packages) Shown above is the demand curve for baseball cards in a perfectly competitive market, Based on the information in the graph, what is the marginal revenue of increasing production from 19 packages to 20 packages? Provide your answer below: MR