
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 catches and marks 60 fish and then releases them back into the lake. On September 1st, he randomly catches 70 fish and finds that 3 of them are marked. He assumes that on May 1st, 25% of the fish in the lake will no longer be there by September 1st (due to death or migration), and that 40% of the fish in the lake on September 1st were not in the lake on May 1st (due to being newly born or just migrated into the lake). He also assumes that the fish caught on September 1st are representative of the entire fish population in the lake. How many fish were in the lake on May 1st?

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