
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]


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Given that $\triangle ABC$ is an acute triangle, vector $\overrightarrow{m} = (\cos(A + \frac{\pi}{3}), \sin(A + \frac{\pi}{3}))$, $\overrightarrow{n} = (\cos B, \sin B)$, and $\overrightarrow{m} \perp \overrightarrow{n}$.

(Ⅰ) Find the value of $A-B$;  
(Ⅱ) If $\cos B = \frac{3}{5}$ and $AC = 8$, find the length of $BC$.

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