
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
If the sum of the first $20$ terms and the sum of the first $50$ terms of a given arithmetic progression are $200$ and $0$, respectively, then the sum of the first $70$ terms is:
A) -400
B) -466.67
C) -500
D) -600

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