Hi Suresh,
Like Activity type, there is a characteristic called Object. This object can be WBS or Network activity in our case.
As I understand your requirement, you want to 3 distinguished materials under a header (kind of), what you can do is that enable Object characteristic just like Activity type. In addition to that, enable Structuring for Object. Specify that Structuring level as 2. (This you can find if you scroll right on that characteristic screen).
Now, check consistency of your profile in ODP2L. Most of the the time, when you enable structuring, this step is required to be done. Try resolving any error if you encounter. Let us know for any difficulty.
So if this is configured correctly, you can see the Activity / WBS in DP91 and total of 120 against it. Under this object, you will see you 3 line items.