I need help with my homework this is only for practice to give us an idea of what our final will be like ASAP my exam is on friday

Consider an industry with 3 firms selling homogeneous products. The cost function, the same for each firm i=1,2,3, is C_i(q_i)=50q_i+300 Demand for the product is P=170-Q. 1. Assume firms compete in quantity . (a) Derive the reaction functions for each firm. (1 point) (b) Derive the equilibrium quantities, price and profits, and show that in equilibrium the industry output is Q*=90. (1 point)