Market shares of all eight firms in an industry are 50 percent, 20 percent, 14 percent, 6 percent, 4 percent, 3 percent, 2 percent, and 1 percent. What is the Herfindahl index?
a. 502 + 202 + 142 + 62 + 42 + 32 + 22 + 12
b. 502 + 202 + 142 + 62
c. the sum of the market shares of the four largest firms
d. 902
e. 90