
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 survey on "spam messages on mobile phones" was conducted. The number of questionnaires collected from units A, B, C, and D formed an arithmetic sequence. From the collected questionnaires, a sample of 100 was drawn, stratified by unit. If 20 questionnaires were drawn from unit B, how many questionnaires were drawn from unit D?

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