
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 a certain entertainment unit, each member can sing or dance at least one of the two. It is known that there are 4 people who can sing and 5 people who can dance. Now, 2 people are selected from them to participate in a social charity performance. Let $\xi$ be the number of people selected who can both sing and dance, and $P(\xi≥1)=\frac{11}{21}$.  
$(Ⅰ)$ Find the total number of members in this entertainment unit.  
$(Ⅱ)$ Find the probability distribution and the expected value $E(\xi)$ of the random variable $\xi$.

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