Multistrike and More Damage from Gems

I am trying to figure out how multistrike's less attack damage applies to the more damage from added fire and Hatred.

I know that say for added fire, if I do 100 phys damage it becomes 39 fire damage.
Upon that 39 fire damage is then my increased phys, elemental, and fire damage.
For an equation of 39*9.514 with just the increased damage.

Now its the less and more damage that confuses me. I know how my 2.18 more phys modifier and 2.28 more elemental modifier will apply. It is how the .64 modifier from multistrike is applied confuses me.

I know it will be one of the following, but I can find nothing that will help me figure out which.

39*9.514*.64*2.18*2.28
or
39*9.514*.64*.64*2.18*2.28

Any help given would be greatly appreciated.

neither

the basic rule is:

all "increased" modifiers from all sources are additive (=summed up into one multiplier)
all more/less modifiers are multipliers

damage = base * (1 + sum_of_all_increased_modifiers) * more1 * more2 * less1 * less2....

Ah thank you that does help clean up my equation, but it didn't answer my question. Does the less attack damage from multistrike apply twice to the elemental damage or just once? Sorry if my original post was vague on that.

once.

It's basically: take all damage values you have without multistrike and multiply them with 0.64.

Thanks for the help.