Three firms, j = 1, 2, 3 compete in a market by choosing quantities

Three firms, j = 1, 2, 3 compete in a market by choosing quantities. Firm 1 is a dominant firm and chooses quantities first while firm 2 and 3 choose quantities simultaneously but after firm 1 has chosen. Firms maximize profit and if firm j produces/offers quantity q it pays the cost C(q) = cq. Products are homogeneous and demand is linear and given by the inverse function P(q1, q2, q3) = 100 https://www.studyhelpus.com/Questions & Answers/compete-in-a-market-by-choosing-quantities/