
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
Point M is inside the plane of $\triangle ABC$, and $\overrightarrow {MA}+ \overrightarrow {MB}+ \overrightarrow {MC}= \overrightarrow {0}$. If D is the midpoint of BC, calculate the value of $\frac {S_{\triangle ABC}}{S_{\triangle MBC}}$.

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