
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 speedboat departs from pier $A$, travels downstream to pier $B$, and continues downstream to pier $C$. After reaching pier $C$, it immediately turns around and travels back upstream to pier $B$, taking a total of 10 hours. If the distance between $A$ and $B$ is 20 kilometers, the speed of the speedboat in still water is 40 kilometers per hour, and the river's current speed is 10 kilometers per hour, find the distance between $B$ and $C$.

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