OSP Service Item has unbit price but volume changes against each FG

Summary:

The client has 1 OSP service item with unit price 2100 but against each FG the rate depends on the volume

for example say an OSP service item has price 2100 for supplier WH PRECAST SDN BHD but the same service item is used for different output
1. 20805-CP1000
2. 20805-CP1001. Against each of these item the service item price depends on volume 1.108 and 1.16

So price for Service item OSP-WHP-21805-PL-200 is 2100*1.108 for 1 unit of FG 20805-CP1000

and price for SErvice item OSP-WHP-21805-PL-200 is 2100* 1.16 for 1 unit of FG 20805-CP1000

How can this be acheived in terms of OSP service item definition and BPA creation