Enchantment mod question

I once saw a table showing how GW rounds off for enchantment mods. (I.E. how many seconds a 10 second enchantment would last with a 10% enchant mod, an 11%, 12%, etc. etc.)

Essentially, if you want that mod for a specialized purpose, it would let you know how much you'd have to spend -- if you'd have to go all out and buy the 20% mod, or if a 16% will do just as well.

I'm trying to figure this out for a PvE orders necro, exactly how high the mod has to be to make orders last 6 seconds as opposed to 5 seconds. And, while I'm at it, how high it has to be to make Blood Renewal last 12 seconds as opposed to 10.



Thanks in advance.