XSLT aggregating XML tag values and storing new tag

Question

I\'m new to xslt and trying to process below XML using XSLT :

F<         


        

Answer 1

Since XSLT variables are immutable, I'm unable perform below operation.

I don't see what variables, immutable or not, have to do with it. This is just straightforward XSLT:

XSLT 1.0