
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 3000 units of a certain product, which came from three production lines: A, B, and C. To check the quality of these products, it was decided to use stratified sampling. If the numbers of units sampled from production lines A, B, and C are $a$, $b$, and $c$ respectively, and $a$, $b$, $c$ form an arithmetic sequence, then the number of products produced by production line B is ____.

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