Purchase group assignment based on plant

Hi,

I have an IDOC that has information on WBS for which a program in SRM has to create purchase order,

The program fetches company code, plant based on WBS element from backend system,

Now I need to know the logic to determine purchase group and delivery address based on plant,

In Org.structure we have assigned unique plant as responsible for each purchase group and Delivery address is assigned as default in plant attributes.

So my query is how to get purchase group and delivery address value based on plant

please provide your inputs

Thanks