Calculate price based on no. of places entered

jquery.seminar-enquiry.js

$(function () {
    var $places = $('#secondaryContent #places'),
        $payment_amount = $('#secondaryContent #payment_amount'),
        singular_amount = 145.00;

    var delay = (function () {
        var timer = 0;
        return function (callback, ms) {
            clearTimeout(timer);
            timer = setTimeout(callback, ms);
        };
    }());

    $places.keyup(function () {
        var VAT = 1.2,
            quantity = $(this).val(),
            price_format = (function () {
                var rgx = /(\d+)(\d{3})/;

                return function (nStr) {
                    var x = String(nStr).split('.'),
                        x1 = x[0],
                        x2 = x.length > 1 ? '.' + x[1] : '';

                    while (rgx.test(x1)) {
                        x1 = x1.replace(rgx, '$1' + ',' + '$2');
                    }

                    return x1 + x2;
                }
            }());

        if ((!isNaN(quantity) && quantity > 0 && quantity < 500) && (!isNaN(singular_amount) && singular_amount > 0)) {
            delay(function () {
                $payment_amount.val(String((singular_amount * quantity) * VAT) + '.00');
            }, 1000);
        }
    });
});