
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 water tank has five pipes. To fill the tank, the first four pipes together take 6 hours; the last four pipes together take 8 hours. If only the first and fifth pipes are opened, it takes 12 hours to fill the tank. How many hours are needed to fill the tank if only the fifth pipe is used?

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