How to set up notification to notify the higher levels in approval

I have set up an approval in request with 3 steps: Approval Level 1 (<1K), Approval Level 2(1K-2K), Approval Level 3(>2K).  How can I also set up the notification such that after level 1 approve for <1K (request status becomes open), level 2 and 3 does not need to approve, but system will send notification to notify the level 2 and level 3. And also, after level 1 and level 2 approve(1K-2K), level 3 does not need to approve, but it will send notification to notify level 3 that request has been open.