Your colleague is working on the following LP problem: Maximize z = -x₁ + x₂ + 2x₃ subject to x₁ + 2x₂ - x₃ ≤ 2, 2x₁ + 3x₂ + x₃ ≤ 6, -2x₁ + 4x₂ + 2x₃ ≤ 8, x₁, x₂, x₃ ≥ 0.
a) The optimal solution is z = 10.
b) The optimal solution is z = 8.
c) The optimal solution is z = 6.
d) The optimal solution is z = 4.