In September 2008, Toyota Motor's Share of the U

In September 2008, Toyota Motor's share of the U.S. auto sales market was 15 percent, Ford's market share was 12.1 percent, GM's was 29.1 percent, Honda's was 10 percent, Nissan's share was 6.2 percent, and Chrysler's market share was 11.1 percent. What is the four-firm concentration ratio in the auto market?

A) 83.5
B) 66.2
C) 67.3
D) 62.3