Minions and IIR

Alright so i've been reading a lot on this but still don't have a clear answer. If a minion with the item rarity gem kills a monster does the rarity of drops add both the player's IIR and the minion IIR or just the minion.

So say the minion has 50% IIR and the player has 200% IIR, are drops by enemies killed by minions 250% IIR?

Minion's total IIR is its own IIR + your IIR.

The correct answer is 250% IIR.

Source: http://pathofexile.gamepedia.com/Rarity

Increased Item Rarity (IIR)
Rarity bonuses are only applied by the person who lands the killing blow to a monster - multiple characters attacking a monster will not stack their item rarity bonuses together. If one of your minions gets a kill, the minion's IIR is added to yours and the total is used. Magic, rare, and unique monsters have an increased item rarity modifier for drops. Rarity bonuses only apply to equipment drops, and will not affect currency.[5]

Increases the chances of an item being magic, rare, or unique.

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If a minion with the item rarity gem kills a monster does the rarity of drops add both the player's IIR and the minion IIR or just the minion.

In your example with Increased Item Rarity, it would apply.
However, if say a Minion (mainly Animate Guardian), has some IIR from a unique (Goldrim) or rare item, and does the kill. The IIR bonus the Animate Guardian gets from Goldrim does not apply, just yours.

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Rarity bonuses are only applied by the person who lands the killing blow to a monster - multiple characters attacking a monster will not stack their item rarity bonuses together. If one of your minions gets a kill, the minion's IIR is added to yours and the total is used.

I am fairly sure this is not true.

Not much philosophy here, you have an increased rarity gem linked to the skill, if you kill an enemy with that skill the rarity bonus gets added to the one your character has, as simple as that.

Item-find bonuses do have a peculiarity, though, as the total bonus isn't a player character property, it's even more global than that and applies to any kill that is in any way attributed to you. However, it accounts only for bonuses your character has, that's why any rarity bonuses a minion could have via items gets ignored, as starsword mentioned. Rarity support gem mot likely works because it doesn't grant a regular minion property but is tied directly to the skill in some other way.