According to the Department of Justice merger guidelines, a proposed merger between two firms may be challenged if the post-merger Hertindahl-Hirschman Index O Alles between 1.500 and 2,600 and the merger raises the Index by 50 points. OB. les between 1,500 and 2,500 and the merger raises the Index by more than 100 points. Oc lies above 2,500 and the merger raises the Index by less than 50 points OD. lies below 1,000 and the merger raises the Index by 100 points