
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 biologist wants to estimate the number of fish in a lake. On May 1st, he randomly caught 60 fish, marked them, and released them back into the lake. On September 1st, he randomly caught 70 fish and found that 3 of them were marked. Assuming that 25% of the fish present on May 1st were no longer in the lake by September 1st (due to death or migration), and that 40% of the fish present in the lake on September 1st were not in the lake on May 1st (due to new births or migration), and that the fish caught on September 1st represent the entire fish population of the lake, how many fish were in the lake on May 1st?

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