Suppose an industry is made up of 16 firms. three firms each sell 12 percent of the industry's total output; another three firms each sell 8 percent; another five firms each sell 5 percent; and the last five firms each sell 3 percent. what is the eight-firm concentration ratio in this industry?
a. 1.40
b. 0.85
c. 0.70
d. 0.40
e. 0.50