Who has the right to decide the amount of mahr to be given by the husband to his wife? How much is the mahr supposed to be? Is a marriage valid without it?

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Check below answers in case you are looking for other related questions:
The marriage contract was done without any mention of the mahr (dowry)
What is the minimum amount of mahr? What is the modern equivalent of the mahr of the Mothers of the Believers?

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Related Answers:
Reducing the mahr is the Sunnah
A Christian woman has the right to ask for a dowry from her Muslim husband
Her husband gave her a mahr of a car that he bought by means of riba; now he wants to take it back so he can buy another car by permissible means
The marriage contract was done without any mention of the mahr (dowry)
What is the minimum amount of mahr? What is the modern equivalent of the mahr of the Mothers of the Believers?

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