
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
A high school Year 1 class (1) and class (2) have 18 and 27 students, respectively, who have signed up to participate in research study courses. By the method of stratified sampling, several students are selected to form a research study group. It is known that 3 students were selected from class (2).  
(Ⅰ) Calculate the number of students in the research study group.  
(Ⅱ) Plan to arrange one exchange activity each in the middle and later stages of the research study, randomly selecting one student from the group to speak each time. Calculate the probability that the students speaking in both activities come from different classes.

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