Problem 4. Consider the non-linear system of ODEs given by y1 = f1 (y1, y2) = -2y1(3 - y2 - y1), y2 = f2 ( y1, y2) = y2( - 4 + y1 + 2y2). 1. Using Mathematica, find all the critical points of the system. (1 mark) 2. Using Mathematica, calculate the linearised system about each of the critical points, and classify the critical points, including type and stability. (2 marks) 3. Using Mathematica, find the nullclines of the system. (1 mark) 4. Using Mathematica, sketch a phase portrait for the non-linear system. Clearly identify each of the critical points and nullclines. (2 marks)