
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 $20$-liter tank is initially filled with a mixture of $10$ liters of water and $10$ liters of alcohol. $5$ liters of this mixture are removed and replaced with pure acetone. This process is repeated three more times. Determine the fraction of the original water that remains in the tank after the four replacements.
- **A)** $\frac{1}{4}$
- **B)** $\frac{9}{16}$
- **C)** $\frac{27}{64}$
- **D)** $\frac{81}{256}$
- **E)** $\frac{125}{256}$

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