Excise Liability

I understood that 'B' stands as jobworker for 'A'

If this is a jobwork process Under rule 57f of excise then either the manufacturer or jobworker any one of them is liable to pay excise on the finished product...

You can go through the enclosed file for more details...

The job worker is the manufacturer and hence liable to pay duty. If however the job worker follows procedure laid down in notification 214/86 or Cenvat Rule (57F4 procedure), he is exempted from paying excise duty.