function loanRepay( form ) {
    var principal = parseFloat(form.principal.value);
    var apr = parseFloat(form.apr.value) / 100;
    var maturity = parseFloat(form.maturity.value);
     
    var monthlyrate = Math.pow(apr + 1, 1/12) - 1;
    var monthlypayment = ( principal * monthlyrate ) / ( 1 - Math.pow(1 + monthlyrate, -maturity) );

    form.repay.value = strRound(monthlypayment, 2);
    form.total.value = strRound(monthlypayment * maturity, 2);
}