(Table) the Table Shows Sales from All 10 Stores in the Grocery

Multiple Choice

(Table) The table shows sales from all 10 stores in the grocery industry. The four-firm concentration ratio is
$\begin{array}{c}\hline {\text { Grocery Store Industry }} \\\begin{array}{|c|c|}\hline \text { Firm } & \begin{array}{c}\text { Sales } \\\text { (S million) }\end{array} \\\hline 1 & 20 \\\hline 2 & 18 \\\hline 3 & 16 \\\hline 4 & 13 \\\hline 5 & 10 \\\hline 6 & 8 \\\hline 7 & 6 \\\hline 8 & 5 \\\hline 9 & 3 \\\hline 10 & 1 \\\hline\end{array}\end{array}$

A) 67.
B) 79.
C) 18.
D) 62.