I can see you getting confused between your Vs and your Ns in the middle of your workings where, for example, V has some closing inventory bought from S. P normally sells to N at a standard gross margin of 30%
I think I would be inclined to bite the proverbial bullet and call them P and S
Besides, it’s only happened once in living memory that the parent and the subsidiary were not P and N
There are more important things to worry about than the examiner’s lexicographic abilities