What is the best response of GC Corp if BIG Q produces, 1,3,5 or 8 units of bran?

GC Corp and BIG Q are big on the cereal market. Both sell bran and demand for bran is given by P=11-Q1-Q2, where Q1 is the amount produced by GC Corp, and Q2 is the amount produced by Big Q. The marginal cost of production are constant and the same for both companies: MC=1.