Exhibit 9-4 Monopolist's demand and cost curves There is a graph with four distinct curves. Quantity of output (in units per hour) is on the horizontal axis from 0 to 13 in increments of 1. Price, costs, and revenue per dose (in dollars) is on the vertical axis from 0 to 200 in increments of 20. A demand curve labeled with D is a straight line that passes through points (0,180), (4,120), (6,90), (8,60), and (12,0). A marginal cost curve labeled MC is positiely sloped line with a slope that increases as quantity increases; it passes through (4,60) and (6,90). A marginal revenue curve labeled MR is a straight line that passes through (0,180), (2,120), (4,60), and (6,0). An upward-facing parabola depicts average total cost (ATC), and it passes through (2.5,140), (6,90), (8,100), and (10,120). As shown in Exhibit 9-4, in order to maximize its profit (or minimize its loss), how much output should the monopoly produce? Group of answer choices 2 units per hour 6 units per hour 8 units per hour 4 units per hour