public static function validate($cardId, $selected, $otp) {
    $card = self::load($cardId);
    if(isset($card['usable'][$selected]) && $card['usable'][$selected] === true) {
      if($card['list'][$selected] == $otp) {
        unset($card['usable'][$selected]);

        self::save($card);
        return true;
      }
    }
    return false;
  }