With an estimated market share of 60%, Atlas is the market leader in an oligopolistic steel industry. The remaining market share is distributed equally between ten companies. Suppose that one of those ten companies, Norton, attempts to gain market share by undercutting the price set by Atlas.

Calculate the "Four Firm Ratio" and Herfindahl-Hirschman Index "HHI" in the above described market and interpret your answer. What is your opinion regarding the effect of Norton's attempt described above on Atlas's market share: will it increase, decrease, or not affected at all? Justify your answer.