
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
Determine the probability that both banknotes are counterfeit given that one of the two randomly selected 100 yuan banknotes from a stack of 20 (which contains 5 counterfeit notes) is verified to be counterfeit upon examination with a money detector.

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