Suppose there are seven firms in a market where the three largest firm

Suppose there are seven firms in a market where the three largest firms supply 20% of the market-clearing quantity and the other four firms supply 10% of the market-clearing quantity. What is the five-firm concentration ratio (i.e.

, the share of total sales controlled by the five largest firms in the market)? A) 60%
B) 70%
C) 80%
D) 90%

ANSWER

C