求助！IR题

lydialee92

Our new 15/12 discount loan is perfect for quick business projects. Customers can borrow an amount up to 80% of the value of their collateral assets at 15% discounted interest and have 12months to repay the loan amount.
A 15/12 loan with amount n rupees is taken out by a business. Select the expressions for the repayment amount ( the sum of the payments made to fully repay the loan)
答案是1.00n。
怎么算的呀？就大神指点！