Int affects Mana Consumption and Casting Time

You have some inconsistent data there I think. 84 + 1 = 85 while 81 + 3 = 84. Also, where did the 85 or 84 come from? One charge of fireball should cost 25 MP with no mp reduction. With rank 1 fire mastery, it should be 20 mp per charge. Therefore, it should be 100 mp in 20 seconds. There is also the question of whether the supposed int bonus would be based off the base mp cost or the mp cost after bonuses. In other words, is it base mp * (1 - fire mastery reduction - int bonus reduction) or is it base mp * (1 - fire mastery reduction) * (1 - int bonus reduction)?