Suppose There Are 100 Firms in an Industry

Multiple Choice

Suppose there are 100 firms in an industry. If the leading firm has a 60 percent market share, the second largest firm has a market share of half the leader's, the third has a market share of half the second's, and the fourth largest has a market share of half the third's, what is the four-firm concentration ratio?

A) 75 percent
B) 85 percent
C) 95 percent
D) 100 percent
E) impossible because their combined market shares exceed 100 percent