Darkray and Snakebite frenzy duration

Can someone calculate for me frenzy charge duration (if there's left any) with darkray + snakebite,9 charges, 72% or 126% inc duration on the tree.

pretty simple, increased/reduced are additive and the base duration is 10s

reduced = 50% + 9*10% = 140%

->

140% reduced + 72% increased = 68% reduced -> 10 * 0.32 = 3.2s
140% reduced + 126% increased = 14% reduced -> 10 * 0.86 = 8.6s

Thanks for the help.