How can we setup Absences approval by Business Unit or Legal Entity

Scenario:

You have 5 Legal Entities (LEs) Each Legal Entity has one Business Unit (BU)

Each BU has a separate HR department representative for approving absences.

I want to setup Absence Approval based on Legal Entity or BU. I implement a HR representative Security based on AOR.

I want to achieve the target that when an employee submits an absence request, it should route Line Manage and after that automatically route to the HR representative that supports to Legal Entity / Business Unit.

How can i achieve that scenario?