
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 fast train and a slow train are traveling towards each other on parallel tracks. The fast train is 420 meters long, and the slow train is 525 meters long. A person on the fast train observes that the slow train passes by in 15 seconds. Determine the time, in seconds, that a person on the slow train observes the fast train passing by.

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