How to determine raw material, wip,fg

Hi,

Please clear my below doubt.

1)For Product A,

2)Raw Material B & C are used,after processing stage 1 they are sent out for another process.

3)Now, when sending out for job order how to invoice it. whether new part no has to be created under semifinished goods or it can be invoiced under Product A.

4) If new part no has to be created under WIP. then when this part comes back how it will be mapped to product A as there are still two more process pending to derive product A.

Thanks in advance.