naive mana cost question

Obviously I am an idiot, please help me figure this out:

Frostblink's gem mouseover says it costs 14 mana (I've been keeping at level 6, since Im unsure if I can afford the upgrade.)

I have two masteries, pay with life instead of 15% of mana and 10% reduced mana costs of skills.

When I socket it, the hotkey mousover says 5 mana, 2 life.
15% of 14 is 2.1, so I pay 2 life -- and I would assume 12 mana, if I did not have the other mastery.
But I do, and I thought I would be paying 10% reduced costs on the 12, which would bring the cost down to 10 or 11?

So why 5 (and not 10)?

Then I socket Second Wind, which is 200%.

The mouse overlay says 15 mana 4 life. I conclude this is correct because 200% is not 5 x 2 = 10 but rather 5 + (200% of 5 or 10) = 15 -- right?

If so, then why am I paying 5 + 200% of 5 = 15 mana and 4 life instead of 15 mana and 2 + (200% of 2 or 4) = 6 life?

Sorry for being such an idiot at basic arithmatic, but I am stumped.

"

seaman wrote:

Calculations with "life instead of % mana" mods are a bit confusing. Also, you missed the mana cost mod on the ring. The calculation order is:

Life cost
14 (base cost)
*0.15 (life instead of 15% mana)
=2

Mana cost
14 (base cost)
*0.9 (10% reduced mana costs)
-7 (ring)
*0.85 (life instead of 15% mana)
=5

Life cost with Second Wind
14 (base cost)
*2 (Second Wind)
*0.15 (life instead of 15% mana)
=4

Mana cost with Second Wind
14 (base cost)
*2 (Second Wind)
*0.9 (10% reduced mana costs)
-7 (ring)
*0.85 (life instead of 15% mana)
=15

Right!
Me idiot. Thank you