HTTP request body to update the Inventory quantity of a single item on Amazon Seller Central

<?xml version="1.0" encoding="utf-8" ?>
<AmazonEnvelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="amzn-envelope.xsd">
<Header>
  <DocumentVersion>1.01</DocumentVersion>
  <MerchantIdentifier>xxxxxxxxxxxxxx</MerchantIdentifier>
  <FulfillmentCenterID>xxxxxxxxx</FulfillmentCenterID>
</Header>
  <MessageType>Inventory</MessageType>
<Message>
  <MessageID>1</MessageID>
  <OperationType>Update</OperationType>
  <Inventory>
  <SKU>ASUSVNA1</SKU>
  <Quantity>8</Quantity>
  </Inventory>
</Message>
</AmazonEnvelope>