Please explain the answer with the required math to get the answer, and an explanation. I do not understand, thank you.

(Figure: Light Bulbs) What price of light bulbs would induce the firms in this diagram to minimize total production costs while maintaining production of 200 million light bulbs? Cost per. light bulb $1.60 MC1 1.40 1.20 MC2 1.00 0.80 0.60 0.40 0.20 20 40 60 80 100 120 140 160 Light bulbs (millions) O $1.00 $0.80 $1.00 for Firm 1, $0.70 for Firm 2 O $0.40