Indented BOM Cost does not report departmental overhead of BORROWED resource

Oracle EBS Release 12.1.3

Solution Requirement:

For the below requirement, should the overhead be kept on the Resource setup or should the overhead be kept on the Department setup?

Business Environment:  Configure To Order manufacturing environment which uses Standard Costing.  The design idea is to define a Model BOM such that the most efficient BOM and Routing is defined for the most efficient departments and resources FOR THE MOST COMMON PRODUCT.  However, variations arise where the most efficient resource is in a DIFFERENT department.  How does the COSTING system ensure that when a variation which needs a DIFFERENT department is manufactured has that department's overhead?