Spiral Volley damage caculation

The description of "Spiral Volley" skill says
"
30% more Damage per Frenzy Charge Consumed
100% more Damage if a Frenzy Charge was Consumed
"
So how much damage do I exactly gain, for example, if I consume 3 Frenzy Charges?
Is it "1 + 100% + 30% * 3 = 290%",
or "(1 + 100%) * (1 + 30% * 3) = 380%",
or "(1 + 100%) * (1 + 30%) * (1 + 30%) * (1 + 30%) = 439.4%"?