Expense Report Approval based on Position Hierarchy?

Summary:

Hi we require to configure position based approvals for Expense Reports.

I have already defined it for Purchasing documents from the Mange Purchasing Document approval Task and is working fine as required, but from BPM it's not clear how to define for Expense Reports.

My position Tree and Job levels are as follows,

Top level - CEO - JOB LEVEL 50
Level 3 - Procurement Division Head - JOB LEVEL 40
Level 2 - Local Procurement Department Head - JOB LEVEL 30
Level 1 - Local Procurement Group A Head - JOB LEVEL 20

Our requirement is to send approval for Level 1 manager of expense report creator and then Level 2 to a Specific User as "A" and Level 3 to a Specific user "B" and Level 4 for CEO