An industry consists of three firms with sales of $200,000, $500,000, and $400,000. a. Calculate the Herfindahl-Hirschman index (HHI). b. Calculate the four-firm concentration ratio (C4). c. Based on the FTC and DOJ Horizontal Merger Guidelines described in the text, do you think the Department of Justice would attempt to block a horizontal merger between two firms with sales of $200,000 and $400,000? Explain.