
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 marine biologist wants to estimate the number of dolphins in a coastal area. On January 1st, she captures 100 dolphins, tags them, and releases them back. On June 1st, she captures another sample of 90 dolphins and finds that 4 of them are tagged. She hypothesizes that only 20% of these dolphins might have left the coastal area by June 1st (due to migration), and that 50% of the dolphins present on June 1st were not in the area on January 1st (due to new arrivals). What is her estimate for the number of dolphins in the coastal area on January 1st?

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