Is an agreement to purchase a commodity by installments with a profit ranging between 25% and 30% considered usury (riba), and is adding a 25% charge to the overdue monthly installment due to the failure to pay the principal on time considered unlawful (haram)?

The transaction mentioned is a Murabaha sale for one who commissions a purchase, and it is permissible on condition that the seller takes possession of the commodity before selling it to the buyer, and then sells it for a known, agreed-upon increase. It is permissible to stipulate that all or some installments become due upon delayed payment. However, it is not permissible to stipulate an increase in the agreed-upon price upon delay, because that is usury (riba).