A merchant borrowed an amount of 18,000 dinars with a simple commercial interest of 10%, and it was agreed with the bank that he would pay the principal of the loan in equal installments at the end of every 3 months, while the interests would be paid in full upon borrowing and the remaining merchant would receive it. That the merchant fulfilled his pledge to pay the installments on time find Calculating the annual general investment rate achieved by the bank in this case