
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
Under the condition of ignoring air resistance, the maximum speed of a rocket $v$ (m/s) is a function of the fuel mass $M$ (kg) and the mass of the rocket (excluding fuel) $m$ (kg), which is $v=2000\ln (1+ \frac {M}{m}).$ When the fuel mass is \_\_\_\_\_ times the mass of the rocket, the maximum speed of the rocket can reach $12000m/s.$ (The exact value is required)

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