suma nie działa w JS

First Parse Variables into Number
var amountBorrowed = Number(document.form.amountBorrowed.value);
var interest = Number(document.form.interest.value) / 100;
var payments = Number(document.form.durationOfPayment.value);
var monthInterest = Number(document.form.interestPerMonth.value);
var totalInt = Number(document.form.totalinterest.value);
Horrible Hamerkop