What happens when you have 2 elements that can shock on the same attack?

A character has Voltaxic Rift, 3 Dragons helmet and an Anger Aura.
How will the whole shock chance and duration be calculated?
From what I gather when the hit shocks the shock duration will be calculated from the combined fire+chaos damage dealt? And in this case shock will be rolled per attack, not per damage type that is eligible to shock?

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battled wrote:

From what I gather when the hit shocks the shock duration will be calculated from the combined fire+chaos damage dealt?

Yes, to get shock duration from a hit you just sum up all damage types that are able to shock. I've seen it asked before somewhere, probably in unique item thread when three dragons showed up.

thx