Ajax pass values from view to controller

so I'm trying to pass some values from my view to the controller, the controller gets a list and returns it.

when I try to get the values from my textboxes etc. they are all undefined... not sure what exactly I'm doing wrong here. pretty new to javascript..

here's the js code

<script type="text/javascript">
$(document).ready(function () {
    $("#getFreeApartements").on('click', function () {

        var amounta = $('#amounta').val();
        var amountc = $('#amountc').val();
        var amountan = $('#animals').val();
        var arr = $('#arrival').val();
        var dep = $('#departure').val();
        var atype = $('#atype').val();


        $.ajax({
            type: 'GET',
            data: { 'amountp': amounta, 'amountc': amountc, 'amountanimals': amountan, 'arrival': arr, 'departure': dep, 'apartmentType': atype },
            url: '@Url.Action("GetFreeApartements", "Bookings")',
            success: function (result) {
                $('freeAp').html(result);
            }
        });
        alert(amounta); // --> return undefined

    });
});

textboxinput field

    <div class="form-group">
        @Html.LabelFor(model => model.Adult, htmlAttributes: new { @class = "control-label col-md-2" })
        <div class="col-md-10" id="amountp" name="amountp">
            @Html.EditorFor(model => model.Adult, new { htmlAttributes = new { @class = "form-control" } })
            @Html.ValidationMessageFor(model => model.Adult, "", new { @class = "text-danger" })
        </div>
    </div>

controller:

        public ActionResult GetFreeApartements(int ap, int ac, int aa, DateTime arr, DateTime dep, ApartmentType type)
    {
 //do some stuff with received values here...
        var freeApartements = db.Apartments.ToList();
        return Json(freeApartements, JsonRequestBehavior.AllowGet);

    }

I also tried serializeArray without any success... I'm not getting any errors in the explorer console.. the function gets called, but values are null.. --> undefined should be the error.

any ideas?