Suppose there are 10 rms in an industry and they each have total sales given in the table below. The 4-rm concentration ratio for this industry is Firm Total Sales 1 $10 million 2 $8 million 3 $6 million 4 $6 million 5 $5 million 6 $5 million 7 $5 million 8 $5 million 9 $5 million 10 $5 million 0 .40 O .60 0 .66 o .30 0 None of these