Def Hp and atk leads and weapons

Can anyone confirm how the leader skills and weapons work together? For example if you have 6 star Carl 40% Hp and 40% def for all melee. Then you put all melee characters with him with weapons saying 30% def and 30% Hp. Does it give those characters 70% def and 70% Hp or does it default to the highest being 40% in this case?
If I could get a fact answer please not someone’s opinion thanks.

The bonuses stack.

Yes, they do indeed stack as per the previous answers in this thread.

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Verified by the combat devs in the aforementioned thread.