
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
Given that $F\_1$ and $F\_2$ are the left and right foci of the ellipse $E: x^2 + \frac{y^2}{b^2} = 1 (0 < b < 1)$, respectively, the line $ℓ$ passing through $F\_1$ intersects $E$ at points $A$ and $B$. If the sequence $|AF\_2|, |AB|, |BF\_2|$ forms an arithmetic progression, determine the length of $|AB|$.

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