Price Quantity Total Revenue (P x Q) Dollars per refrigerator) (Refrigerators per year) (Dollars per year) 200 0 150 200 30,000 100 400 40,000 50 600 30,000 m 800 0 The graph below plots the firm's total revenue curve: that is, the relationship between quantity and total revenue given by the two right columns in the table above. The five choices are also labeled. Finally, two black lines are shown; these lines are tangent to the green curve at points B and D. 50 DO TOTAL REVENUE (Thousands of dollars per year) A E 100 200 300 400 600 700 QUANTITY (Refrigerators per year) Using the information on the slope of the lines tangent to the curve at points B and D, plot the slope of the total revenue curve on the graph below. (As it turns out, it's a straight line, so the two points you plot will determine a line. (? 125 O 100 Slope of TR 75 REVENUE (Dollars per refrigerator) -75 -100 100 200 300 400 500 600 700 800 QUANTITY (Refrigerators per year) The total revenue curve reaches its maximum at a quantity of refrigerators per year. At this point, the slope of the total revenue curve is