
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
The number of different sampling results when using a stratified random sampling method with proportional allocation to sample 60 students from junior high school and senior high school sections with 400 and 200 students respectively is how many combinations of ${C}_{400}^{x}•{C}_{200}^{y}$?

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