
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 $A=\{x|a\leqslant x\leqslant a+3\}$, $B=\{x|x < -6 \text{ or } x > 1\}$.

(I) If $A\bigcap B=\varnothing$, find the range of $a$;

(II) If $A\bigcup B=B$, find the range of $a$.

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