How to define Approval Rules using Cost Center Rule set without ignoring the Expense Report Rule set

Summary:

Cost Center Rule and Expense Report Rule set cannot be used at the same time.

Content (required):

We previously implemented Fusion Expense to a Business Unit and used the Expense Report Rule set as their approval flow for expense reimbursement. Currently, we are implementing Fusion Expense to another Business Unit under the same instance and they will be using Cost Center Rule as their approval flow. However, we receive this error "The request operation failed with the business rules defined for ExpenseReportRuleSet" if we enable both approval rules. We need to ignore the Expense Report Rule set participant first before we can make the Cost Center Rule set work.