1117 Market Company share AT &T 20% Verizon 30% Wireless T-mobile 15% Sprint Nextel 10% Other (5 25% firms) a. Compute the four-firm concentration ratio. Show your work. (2pts) b. Compute the HHI before the merger. Show your work. (2pts) c. Use the information in the section "The Department of Justice and FTC Merger Guideline," to predict whether the Department of Justice and the FTC would be likely to approve a merger between AT&T and T-Mobile. Briefly explain your reasoning. (3pts)