Buckeye Furniture produces tables and chairs, earning $120 profit per table and $80 profit per chair. Each table and chair goes through three stages in the manufacturing process: assembly, finishing, and inspection. Each table requires 3 hours of assembly, 2 hours of finishing, and 1 hour of inspection. Each chair requires 2 hours of assembly, 2 hours of finishing, and 1 hour of inspection. Every week there are 200 hours of assembly time available, 180 hours of finishing time, and 40 hours of inspection time.

The decision variables in the model are X₁ for the number of tables and X₂ for the number of chairs.

Which of the following would be a necessary constraint in the problem?

X₁ + X₂ 40

X₁ + X₂ 200

X₁ + X₂ 180

120X₁ + 80X₂ 1000

none of the above