Expenditure Type Name is same but Expendi rate is different as per Customer site in Project Billing

Scenario:

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One customer has different site but there is different site has different rate and Service charge for particular Expenditure.

Expenditure Type Name is same but Expenditure rate and Service charge are Different for Particular Site.

Requirement:

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when I am creating one Contract (For One Customer) for Customer, billing Rate should Pick different customer site as per defined rate in the Rate schedule.

When I am creating Contract Billing there is Option billing Plan(i.e bill Rate Invoice or Burden Schedule Invoice or Cost Reimbursement Invoice).

if Using Bill rate Invoice for Contract Billing so Invoice generate based on which Rate schedule associated in Bill plan for that Contract.