
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 left focus $F$ of the ellipse $C$: $$\frac {x^{2}}{a^{2}}$$+ $$\frac {y^{2}}{b^{2}}$$\=1 ($a>b>0$), a line is drawn through the upper endpoint $B$ of $C$ and intersects the ellipse at another point $A$. If $|BF|=3|AF|$, find the eccentricity of $C$.

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