If There Are 500 Firms in an Industry, and the Four-Firm

Multiple Choice

If there are 500 firms in an industry, and the four-firm concentration ratio is 90 percent, then

A) 496 firms account for the remaining 10 percent of sales
B) the industry must be monopolistic competition
C) the 4 firms each have 90 percent market share
D) the top four firms are a monopoly
E) the leading four firms receive 10 percent of industry profit