
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 the sets $A=\{x \mid \frac {2-x}{3+x} \ge 0\}$, $B=\{x \mid x^2 - 2x - 3 < 0\}$, $C=\{x \mid x^2 - (2a+1)x + a(a+1) < 0\}$.
(Ⅰ) Determine the sets A, B, and $A \cup B$;
(Ⅱ) If $C \subseteq (A \cap B)$, find the range of the real number a.

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