The area surrounded by the blue line is the feasible region of the linear programming problem ${\displaystyle \min\{300x_{1}+500x_{2}\;|\;x_{1}+2x_{2}\leq 170,\;x_{1}+x_{2}\leq 150;\;x_{1},x_{2}\geq 0\}.}$

The red lines are potential lines of the objective functions, i.e., all points on such a red lines have the same objective value. The optimal value is 49000, and it is attained at the unique optimal solution (130,20).

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