Consider the diagram below depicting the revenue and cost conditions faced by a monopolistically competitive firm, and then answer the following questions. MC $70 $65 $60 $55 $50 $45 8 $40 $35 $30 $25 $40 ATC $32.50 Price and costs $25 $20 $14.30 Demand $15 $10 $5 MR 0 Quantity a. According to the diagram, the profit-maximizing output level is O 4.0 units. O 3.0 units. O 2.5 units. 45 units