3. Ten firms compete in a market to sell product X. The total sales of all firms selling the product are $2,000,000. Ranking the firms' sales from highest to lowest, we find the top four firms' sales to be $220,000,$180,000,$160,000, and $120,000, respectively. Calculate the four-firm concentration ratio in the market for product X. a) Calculate the Herfindahl-Hirschman index (HHI). b) Calculate the four-firm concentration ratio (C4)