Someone appointed him to buy something for him; is it permissible for him to increase the price without that person’s knowledge?

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Check below answers in case you are looking for other related questions:
His friends ask him to buy computers for them and he adds a profit for himself
If his relatives want particular types of perfume, is it permissible for him to buy them and sell them to them?

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Related Answers:
Ruling on brokerage
He was asked to sell the product for a specific price but he is selling it for more and keeping the difference
Ruling on an employee and agent of the company owner taking a commission on sales
His friends ask him to buy computers for them and he adds a profit for himself
If his relatives want particular types of perfume, is it permissible for him to buy them and sell them to them?

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