/**
  * @param Cart $cart
  * @param $areaId
  * @return |null
  */
 protected function getSlicePostage(Cart $cart, Country $country)
 {
     $config = self::getConfig();
     $currency = $cart->getCurrency();
     $areaId = $country->getAreaId();
     $query = CustomDeliverySliceQuery::create()->filterByAreaId($areaId);
     if ($config['method'] != CustomDelivery::METHOD_PRICE) {
         $query->filterByWeightMax($cart->getWeight(), Criteria::GREATER_THAN);
         $query->orderByWeightMax(Criteria::ASC);
     }
     if ($config['method'] != CustomDelivery::METHOD_WEIGHT) {
         $total = $cart->getTotalAmount();
         // convert amount to the default currency
         if (0 == $currency->getByDefault()) {
             $total = $total / $currency->getRate();
         }
         $query->filterByPriceMax($total, Criteria::GREATER_THAN);
         $query->orderByPriceMax(Criteria::ASC);
     }
     $slice = $query->findOne();
     $postage = null;
     if (null !== $slice) {
         $postage = new OrderPostage();
         if (0 == $currency->getByDefault()) {
             $price = $slice->getPrice() * $currency->getRate();
         } else {
             $price = $slice->getPrice();
         }
         $price = round($price, 2);
         $postage->setAmount($price);
         $postage->setAmountTax(0);
         // taxed amount
         if (0 !== $config['tax']) {
             $taxRuleI18N = I18n::forceI18nRetrieving($this->getRequest()->getSession()->getLang()->getLocale(), 'TaxRule', $config['tax']);
             $taxRule = TaxRuleQuery::create()->findPk($config['tax']);
             if (null !== $taxRule) {
                 $taxCalculator = new Calculator();
                 $taxCalculator->loadTaxRuleWithoutProduct($taxRule, $country);
                 $postage->setAmount(round($taxCalculator->getTaxedPrice($price), 2));
                 $postage->setAmountTax($postage->getAmount() - $price);
                 $postage->setTaxRuleTitle($taxRuleI18N->getTitle());
             }
         }
     }
     return $postage;
 }