Question regarding Magic loss through lowered Essence, Is it a modification or effective loss? Options

[StevenAngier]

So, while discussing the Chummer Character Generator the question arose what exactly happens if you lose your Magic rating through Essence loss.

AFAIS there are two possible options.

a) You rating is simply lowered in every regard. Thus, if you get the chance to raise it again you have to pay the karma cost of the new rating.

Example?
You have magic 4. It gets lowered to 3 as you got some augmentations implanted. Next time you want to raise Magic back to 4 you have to pay 20 Karma. (New Rating * 5)


or


b) Your "effective" rating is lowered while the rating for karma cost calculations stays the same. If you want to raise it again you have to pay the karma cost for raising your "old" rating.

Example?
You have magic 4. It gets lowered to 3 as you got some augmentations implanted. Next time you want to raise Magic back to 4 you have to pay 25 Karma. Without Essence loss you would have gotten a rating of 5 so it would be 5 * 5 Karma.


What's now the ruling on that? Which of those two options is the right one? Is there any clear ruling on that?