The correct objective function is
min 12x₁₁ + 9x₁₂ + 8x₂₁ + 5x₂₂
min 5x₁₁ + 8x₁₂ + 5x₂₁ + 9x₂₂
min 5x₁₁ + 8x₁₂ + 9x₂₁ + 12x₂₂
min 5x₁₁ + 8x₁₂ + 9x₂₁ none of the above

Q&A Education