
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
In the table tennis singles final between Player A and Player B, a best-of-five game system is used. The probability of Player A winning each game is $\frac{2}{3}$, and that of Player B winning each game is $\frac{1}{3}$. Determine the probability of an upset, in which Player B wins the championship.

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