
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
(12 points) Given the universal set $U=\{1,2,3,4,5,6,7,8,9,10,11,13\}$, set $A=\{2,4,6,8\}$, and set $B=\{3,4,5,6,8,9,11\}$, find:  
(1) $A \cup B$  
(2) $C_U A$  
(3) $C_U (A \cap B)$  
(4) $A \cup (C_U B)$

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