Any Profession How Does Ingredient Effectiveness Work?

Pretty much title. I was thinking about it and I realized I had no idea so I will break it down in to two main questions:

1: Is it additive or multiplicative?
For example, let's say you have a potato ingredient that give 10% xp bonus and a 30% buff and a 40% buff that are both effecting it.
If it was additive the final xp bonus would be calculated like this: 10 * (1 + .3 + .4) = 10 * 1.7 = 17% xp bonus.
If it was multiplicative the final xp bonus would be calculated like this: 10 * 1.3 * 1.4 = 18.2% xp bonus.

On Wynndata it seems to be additive in some rudimentary tests but I want to make sure

2: How do multiple ingredient effectiveness ingredients interact?
This one I have legit no clue. On Wynndata it seems like they don't effect each other at all. Is this how it works in game? I could figure this out with some experimenting in game but I figured if someone has already done the testing they wouldn't mind sharing the results.

 

It's additive.

If you're asking about how effectiveness ingredients interact with other effectiveness ingredients, ingredient effectiveness doesn't affect ingredient effectiveness.

 

That is exactly the information I needed. Thank you!

 

Extra info:
1) ingredient effectiveness doesn't affect durability or duration
2) If you use wynndata for crafting items, it can get ingredeitn effectiveness calculations wrong. (wynndata discord bug report, wynndata recipe link)