
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
Let $\triangle ABC$ be an obtuse triangle with sides $a$, $b$, and $c$ opposite angles $A$, $B$, and $C$, respectively, satisfying $2a\sin A=(2b- \sqrt {3}c)\sin B+(2c- \sqrt {3}b)\sin C$.  
(I) Find the size of angle $A$;  
(II) If $a=2$, $b=2 \sqrt {3}$, find the area of $\triangle ABC$.

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