What is the correct constraint for node $2$ in the following diagram?

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Node $1$ connects to Node $2$ which connects to Node $3.$ The coefficients at each node are $-200,+100,$ and $+50,$ respectively.

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Group of answer choices

X$12+$ X$23=100$

X$12$ X$23<=100$

$$X$12+$ X$23>=100$

X$12$ X$23>=100$