Spell Fatigue for 100+ spells

[Tichy]

I apologize if this has been asked and answered before, but I'm wondering how to calculate fatigue for a bf spell that requires gems to cast.

Does the number (say 100 for some standard battlefield summons) get entered into the ((1/(1+skill-requirement))*fatigue)+encumbrance calculation, or does the use of a gem change the "fatigue" number you calculate on?

So an A1 mage casting Summon Lesser Elemental:
((1/1+2-1)*100)+enc = 1/2*100+enc = 50+enc

Is this right?

(I set requirement to 2 assuming the gem gave him the level...or would he need to spend 2 gems to get that benefit? 1 for the spell, 1 for the level boost, which an A1 mage couldn't do because he can only use as many gems as he has levels.)

Thanks.