Hide buttons and Enable Other with ajax

I have a page and it shows a modal with 2 buttons, one of confirmation and another of canceling, according to the code Below: Within this modal I have a DIV <div class="resp"></div> This div I get a response from a page in PHP , I would like to hide the 2 BUTTONS I have inside this modal and after receiving the response from the php page show another button to close this modal. How can I do this?

<!-- Modal -->
<div class="modal fade" id="md-default" tabindex="-1" role="dialog">
   <div class="modal-dialog">
      <div class="modal-content">
         <div class="modal-header">
            <button type="button " class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
         </div>
         <div class="modal-body">
            <div class="text-center">
               <div class="i-circle primary"><i class="fa fa-check"></i></div>
               <h4>Confirma o envio?</h4>
               <div class="resp"></div>
               <p></p>
            </div>
         </div>
         <div class="modal-footer">
            <button type="button" class="btn btn-default btn-flat" data-dismiss="modal">Cancelar</button>
            <button type="submit" class="btn btn-primary btn-flat enviar" >Sim</button>
         </div>
      </div>
      <!-- /.modal-content -->
   </div>
   <!-- /.modal-dialog -->
</div>
<!-- /.modal -->

Ajax call code

<script>
     $('.formulario').submit(function() {
         var form_data = new FormData();
         form_data.append('fileUploadAudio', $('input.fileUploadAudio').prop('files')[0]);
         form_data.append('titulo', $('input.titulo').val());
         form_data.append('mensagem', $('textarea.mensagem').val());
         form_data.append('tipo_notificacao', $('input.tipo_notificacao').val());
         $.ajax({
             url: 'postar.php', // caminho para o script que vai processar os dados
             type: 'POST',
             data: form_data,
             cache: false,
             contentType: false,
             processData: false,
             success: function(response) {
                 $('.resp').html(response);
             },
             error: function(xhr, status, error) {
                 alert(xhr.responseText);
             }
         });
         return false;
     });
  </script> 

Test page: LINK