A line graph showing the social and private costs of pollution." A line graph showing the social costs and private costs of pollution. The x-axis is labeled Quantity (units per time period). The y-axis is labeled Price or Cost (dollars per unit). Price equals MR. There is a line extending from the y-axis that remains constant for all quantities. The line labeled Social MC intersects this constant line at a quantity of 200. The line labeled Private MC intersects the constant line at a quantity of 320. The Social MC and Private MC line curve slightly, but run parallel with each other. The Social MC line is inside of the Private MC line." Refer to the figure. If the firm chooses a production method that results in zero external costs, the rate of output will be Multiple Choice 320 units per time period. 200 units per time period. greater than 320 units per time period. less than 200 units per time period