Problem 4 data: “a). The equation Qa = 1/2(12-Qb) is the so-called reaction function of duopolist A in a Cournot model because given the value of Qb’Qa gives the best profit-maximizing level of sales of oligopolist A (reaction functions are derived in the first section of the appendix to this chapter).”The reaction function of duopolist A is QA = (12-QB)/2 (1)The reaction function of duopolist B is QB = (12-QA)/2 (2).