They inherited wealth from their father and invested it in some business; how should they pay zakaah?

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Check below answers in case you are looking for other related questions:
Is zakaah due on manufacturing equipment?
Each partner must pay zakaah on his share of the profits from mudaarabah (partnership)

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Related Answers:
Detailed discussion of zakaah on shares
She died and left behind a mother, two sisters and a husband
His father killed his mother; can he take the inheritance from him on the basis that it is diyah (blood money)?
Is zakaah due on manufacturing equipment?
Each partner must pay zakaah on his share of the profits from mudaarabah (partnership)

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