
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
The service life $X$ (unit: years) of the battery of a certain brand of mobile phone follows a normal distribution $N(4, \sigma^2)$ ($\sigma > 0$), and the probability that the service life is at least 2 years is 0.9. Calculate the probability that the battery of this brand of mobile phone will be used for at least 6 years.

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