D How would you calculate a four-firm concentration ratio? O By dividing the market share of the largest firm by the market share of the smallest firm. O By adding the market shares (expressed as percentages) of the four largest firms. O By calculating the square root of the market shares of the four largest firms. O By multiplying the market shares of four random firms. Question 4 How would you calculate the HHI for an industry? O By summing the market shares for each firm in the industry and multiplying by .2. O By summing the squares of the market share of each firm in the industry. O By multiplying industry sales by .77. O By gathering data on total sales of the firms in the industry and dividing the sum by 7