Similar spell bonuses

If you have multiple spells that would count as "similar spells" when inventing a new spell, do you add only the highest bonus from them, or all of the bonuses together?

e.g. say i have a group of similar spells, a lvl 25, lvl 35 and lvl 10. They all count as similare to each other and to the new spell i am researching.

Do i get a +7 bonus (for the lvl 35 spell) or a +14 bonus (for all three).

Obviously this allows some truly huge bonuses if we use the latter method. That said, it does allowa mage to specialise and do really quite well at a certain kind of magic. I quite like the idea of a mage who has "mastered" teleportation spells, or who has a whole series of powerful CrIg spells that create fiery dragons to attack his foes. Very nice thematically.

Check page 101 of the core rules.

First paragraph: