Magento 2: Free shipping should not work after applying discount coupon and total less than $50?

I want to apply free shipping for subtotal more than $50 and it’s working fine. but if customer applied any discount coupon then free shipping should not apply because grand total is less than $50. For now, Free shipping still applying because Subtotal is still greater than $50.

Can anyone help me how to remove free shipping if Grand total less than $50 after applying discount coupon?

Here is my code:

public function collectRates(RateRequest $request)
    {
        if (!$this->getConfigFlag('active')) {
            return false;
        }

        // exclude Virtual products price from Package value if pre-configured
        if (!$this->getConfigFlag('include_virtual_price') && $request->getAllItems()) {
            foreach ($request->getAllItems() as $item) {
                if ($item->getParentItem()) {
                    continue;
                }
                if ($item->getHasChildren() && $item->isShipSeparately()) {
                    foreach ($item->getChildren() as $child) {
                        if ($child->getProduct()->isVirtual()) {
                            $request->setPackageValue($request->getPackageValue() - $child->getBaseRowTotal());
                        }
                    }
                } elseif ($item->getProduct()->isVirtual()) {
                    $request->setPackageValue($request->getPackageValue() - $item->getBaseRowTotal());
                }
            }
        }

        // Free shipping by qty
        $freeQty = 0;
        if ($request->getAllItems()) {
            $freePackageValue = 0;
            foreach ($request->getAllItems() as $item) {
                if ($item->getProduct()->isVirtual() || $item->getParentItem()) {
                    continue;
                }

                if ($item->getHasChildren() && $item->isShipSeparately()) {
                    foreach ($item->getChildren() as $child) {
                        if ($child->getFreeShipping() && !$child->getProduct()->isVirtual()) {
                            $freeShipping = is_numeric($child->getFreeShipping()) ? $child->getFreeShipping() : 0;
                            $freeQty += $item->getQty() * ($child->getQty() - $freeShipping);
                        }
                    }
                } elseif ($item->getFreeShipping()) {
                    $freeShipping = is_numeric($item->getFreeShipping()) ? $item->getFreeShipping() : 0;
                    $freeQty += $item->getQty() - $freeShipping;
                    $freePackageValue += $item->getBaseRowTotal();
                }
            }
            $oldValue = $request->getPackageValue();
            $request->setPackageValue($oldValue - $freePackageValue);
        }

        if (!$request->getConditionMRName()) {
            $conditionName = $this->getConfigData('condition_name');
            $request->setConditionMRName($conditionName ? $conditionName : $this->defaultConditionName);
        }

        // Package weight and qty free shipping
        $oldWeight = $request->getPackageWeight();
        $oldQty = $request->getPackageQty();

        $request->setPackageWeight($request->getFreeMethodWeight());
        $request->setPackageQty($oldQty - $freeQty);

        /** @var MagentoShippingModelRateResult $result */
        $result = $this->rateResultFactory->create();
        $zipRange = $this->getConfigData('zip_range');
        $rateArray = $this->getRate($request, $zipRange);

        $request->setPackageWeight($oldWeight);
        $request->setPackageQty($oldQty);

        $foundRates = false;

        foreach ($rateArray as $rate) {
            if (!empty($rate) && $rate['price'] >= 0) {
                /** @var MagentoQuoteModelQuoteAddressRateResultMethod $method */
                $method = $this->resultMethodFactory->create();

                $method->setCarrier('matrixrate');
                $method->setCarrierTitle($this->getConfigData('title'));

                $method->setMethod('matrixrate_' . $rate['pk']);
                $method->setMethodTitle(__($rate['shipping_method']));

                if ($request->getFreeShipping() === true || $request->getPackageQty() == $freeQty) {
                    $shippingPrice = 0;
                } else {
                    $shippingPrice = $this->getFinalPriceWithHandlingFee($rate['price']);
                }

                $method->setPrice($shippingPrice);
                $method->setCost($rate['cost']);

                $result->append($method);
                $foundRates = true; // have found some valid rates
            }
        }

        if (!$foundRates) {
            /** @var MagentoQuoteModelQuoteAddressRateResultError $error */
            $error = $this->_rateErrorFactory->create(
                [
                    'data' => [
                        'carrier' => $this->_code,
                        'carrier_title' => $this->getConfigData('title'),
                        'error_message' => $this->getConfigData('specificerrmsg'),
                    ],
                ]
            );
            $result->append($error);
        }

        return $result;
    }

    /**
     * @param MagentoQuoteModelQuoteAddressRateRequest $request
     * @param bool $zipRange
     * @return array|bool
     */
    public function getRate(MagentoQuoteModelQuoteAddressRateRequest $request, $zipRange)
    {
        return $this->matrixrateFactory->create()->getRate($request, $zipRange);
    }

    /**
     * @param string $type
     * @param string $code
     * @return array
     * @throws MagentoFrameworkExceptionLocalizedException
     */
    public function getCode($type, $code = '')
    {
        $codes = [
            'condition_name' => [
                'package_weight' => __('Weight vs. Destination'),
                'package_value' => __('Order Subtotal vs. Destination'),
                'package_qty' => __('# of Items vs. Destination'),
            ],
            'condition_name_short' => [
                'package_weight' => __('Weight'),
                'package_value' => __('Order Subtotal'),
                'package_qty' => __('# of Items'),
            ],
        ];

        if (!isset($codes[$type])) {
            throw new LocalizedException(__('Please correct Matrix Rate code type: %1.', $type));
        }

        if ('' === $code) {
            return $codes[$type];
        }

        if (!isset($codes[$type][$code])) {
            throw new LocalizedException(__('Please correct Matrix Rate code for type %1: %2.', $type, $code));
        }

        return $codes[$type][$code];
    }

    /**
     * Get allowed shipping methods
     *
     * @return array
     */
    public function getAllowedMethods()
    {
        return ['matrixrate' => $this->getConfigData('name')];
    } ```