Consider a linear programming model with three objective functions, the first objective function value needs to greater or equal to 15; the second objective function value needs to greater or equal to 5; the third objective function value needs to greater or equal to 6. Assume the preferences of the decision maker is 1>2>3. Reformulate the model as a goal programming model, Max 3x1+5x2 Max 2x1-3x2 Min x1+x2 St. x1+2x2