Increased Price
Question :

I was requested by a friend to buy a product for him. Is it permissible for me to add a margin for myself and give him the increased price?

Answer :

It is prohibited to do so, without his consent.

Gold Rings
Question :

If a man had gold rings in the past and now realizes that they cannot be worn by him, can he sell them or exchange them for women’s gold jewelry?

Answer :

Yes, it is permissible.

Keeping the Change
Question :

I work in a store as a cashier, and sometimes a customer tells me to keep the change if he gives me more money, so do I have the option of keeping the change for the store or taking it for myself?

Answer :

If it was understood that the customer paid the money for you, then you can take it. If he intended to give it to the store, then it should be given to the store.