subscribe to mailchimp list with double opt in

SubscribeToMailchimpListAJAX

function signupMailchimp() {

            var d = "FIRSTNAME={0}&LASTNAME={1}&EMAIL={2}".format
            (
                encodeURIComponent($("#FirstName").val()),
                encodeURIComponent($("#LastName").val()),
                encodeURIComponent($("#Email").val())
            );

            if ($("form.login").valid()) {
                $.ajax({
                    type: "GET",
                    url: "https://mogy.us11.list-manage.com/subscribe/post-json?u=UID&id=LISTID&c=?",
                    data: d,
                    dataType: 'json',
                    contentType: "application/json; charset=utf-8",
                    error: function (err) {
                        mogy.cerror("Mailchimp error.");
                    },
                    success: function (data) {
                        if (data.result != "success") {
                            mogy.cerror("Mailchimp failed.");
                        } else {
                            mogy.clog("Mailchimp passed.");
                        }
                    }
                });
            }
        }