Development

I have to design a test plan for an app and below is the requirement
Run a thread for 1 user for 55 minutes and in between after the thread starts I need to run another user after 30 minutes.
Can you give any suggestions on how can design and what kind of threadGroup can i use?
Update: I have two groups, the first group will start and run for 120 minutes and the second group of users will start after 30 minutes.

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