In order to calculate the Herfindahl-Hirschman Index, _____ Question 1 options: a) the market shares of the four largest firms in an industry need to be added. b) the market shares of all firms in an industry need to be known. c) the market shares of any four firms in an industry need to be added. d) the market shares of the four largest firms in an industry need to be squared and added. e) the market shares of all firms in an industry do not need to be known