Suppose the Federal Reserve is considering the applications of four different banks to merge with other banks. Given the level of the new HHI and the change in the HHI shown below, in which case could the Fed challenge the merger? New HHI = 1,900; change in HHI = 150 New HHI = 1,500; change in HHI = 400 New HHI = 1,200; change in HHI = 700 New HHI = 1,850; change in HHI = 250