sample code for private loand applying compound monthly interest rate.

I need a formula for private loan. - THIS IS NOT A BIG PROGRAM. - I JUST NEED SAMPLE FORMULA WITHOUT ANY USER INTERFACE. This loan is appling compound monthly interest rate. sample need to display in USD based in javascript or C# code 1. basically this private loan is working like this 1) borrower can make a payment at anytime. they need to pay at least accumulated interest (we need to display interest total as of payment date) 2) next payment will be reduced by previous payment. 2. please give me a exact number with this sample. 1) case a. lender gave $4,000 on 2/10/2016 with monthly rate 4% with 12 terms b. write initial monthly payment with this condition c. borrower want to check his balance on 3/20/2016 (display divided by principle and interest as of this day) d. borrower made a payment $300 on 2/10/2016. wirte remain principle and interest after this payment. - display changed monthly payment e. borrower made a payment $700 on 3/30/2016. wirte remain principle and interest after this payment. - display changed monthly payment f. borrower made a payment $200 on 4/5/2016. wirte remain principle and interest after this payment. - display changed monthly payment g. borrower want to check his balance on 6/25/2016. wirte principle and interest on this day h. borrower want to pay off as of 6/28/2016 i. calculate total profit made by this loan.