I have problem One plz help mein problem 2

The Justice Department has been asked to review a merger request for a market with the following four firms. What is the HHI for the existing market? If Firm A acquires Firm D, what will be the impact on the market's level of concentration? If Firm C acquires Firm D, what will be the impact on the market's level of concentration? What is likely to be the Justice Department's response to the two merger applications? Consider a market that has three firms with the following market shares: Firm A = 35% Firm B = 41% Firm C = 24% Suppose Firm A wants to acquire firm C so that the post-acquisition market would exhibit the following shares: A + C = 76% B = 24% Calculate the pre-and post-merger HHI and the change in the HHI resulting from the merger. According to Department of Justice guidelines, is this merger likely to be challenged? Explain and substantiate your response