
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
A factory produced $16800$ units of a certain product. These products came from three production lines, labeled A, B, and C. In order to inspect the quality of this batch of products, a stratified sampling method is decided to be used. It is known that the number of units sampled from production lines A, B, and C form an arithmetic sequence. Find the number of units produced by production line B.

Present the answer in LaTex format: \boxed{Your answer}
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