
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
Xiao Ming's family's monthly water bill is never less than 15 yuan. The water company's pricing standard is as follows: if a household uses no more than 5 cubic meters per month, the charge is 1.8 yuan per cubic meter; if a household uses more than 5 cubic meters per month, the charge for the excess part is 2 yuan per cubic meter. What is the minimum monthly water usage for Xiao Ming's family?

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