Can you help please

4. Three oligopolists operate in a market with inverse demand given by p(q) = a q, where q = q1 + (12 + (13, and (11- is the quantity produced by rm 2' = 1, 2, 3. Each rm has a constant marginal cost of production, c and no xed cost. The rms choose their quantities dynamically as follows: (1) Firm 1, who is the industry leader, chooses (11 2 0; (2) Firms 2 and 3 observe (11 and then simultaneously choose (12 and ((3, respectively. (a) How many proper subgames does this dynamic game have? (b) What is the subgame perfect equilibrium of this game