
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 monthly salaries (in yuan) of 5 staff members in an office are $x_1$, $x_2$, $x_3$, $x_4$, $x_5$, respectively. Their average monthly salary is 3500, and the variance is 45. Determine the mean and variance of their salaries next month, assuming each person's monthly salary increases by 100 yuan.

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