Marginal Cost Analysis Chart: ProPhone Blazer Quantity of Phones Price (in whole dollars) Total Revenue Marginal Revenue Total Cost Marginal Cost Profit (or loss) 0 220 0 0 90 0 1 200 200 200 170 80 2 180 360 160 200 30 3 160 480 120 290 90 4 150 600 120 340 50 5 140 700 100 400 60 6 135 810 90 500 100 7 130 910 100 620 120 The owner of ProPhone has charted the company's marginal revenue and marginal cost for its latest line of smartphones, the Blazer. Use the chart to calculate the company's profit. What is the difference between marginal cost and marginal revenue at the point when profits are maximized on the chart? a. 10 b. 20 c. 30 d. 40