Maximize $Z = 15X_1 + 20X_2$ subject to $$\begin{array}{l} 12X_1 + 4X_2 \geq 36 \\ 12X_1 − 6X_2 \leq 24 \\ X_1, X_2 \geq 0 \end{array}$$

The above linear programming problem has

- infeasible solution
- unbounded solution
- alternative optimum solutions
- degenerate solution