
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 locomotive approaching with a speed of $20 \mathrm{~m/s}$ sounded its whistle, and it was heard by a person standing at the railway crossing 4 seconds before the train arrived. How far was the locomotive when it started whistling? (The speed of sound is $340 \mathrm{~m/s}$.)

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