How to calculate interest for a loan using diminishing balance method?

I have availed a loan for Rs. 43475/- and repaid first installment of Rs.1835/- . From 2nd to 19th installments Rs.1735/- paid. On 20th installment the balance amount of loan i.e. Rs. 8675/-. I request to inform how much interest to be paid after repayment of entire loan amount of Rs. 43475/-.