How to add queue item in certain queue named Gold with known guid id?

I am using a plugin in CRM

How to add queue item in certain queue named Gold with known guid id?

My Code:

public void Execute(IServiceProvider serviceProvider)
        {
            // Extract the tracing service for use in debugging sandboxed plug-ins.
            // If you are not registering the plug-in in the sandbox, then you do
            // not have to add any tracing service related code.
            ITracingService tracingService = (ITracingService)serviceProvider.GetService(typeof(ITracingService));

            // Obtain the execution context from the service provider.
            IPluginExecutionContext context = (IPluginExecutionContext)serviceProvider.GetService(typeof(IPluginExecutionContext));

            // The InputParameters collection contains all the data passed in the message request.
            if (context.InputParameters.Contains("Target") && context.InputParameters["Target"] is Entity)
            {
                // Obtain the target entity from the input parameters.
                Entity entity = (Entity)context.InputParameters["Target"];

                // Verify that the target entity represents an entity type you are expecting. 
                // For example, an account. If not, the plug-in was not registered correctly.
                if (entity.LogicalName != "incident")
                    return;

                // Obtain the organization service reference which you will need for
                // web service calls.
                IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
                IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);

                try
                {
                    // Plug-in business logic goes here.
                    if (context.MessageName == "Create")
                    {
                        var customerid = ((EntityReference)entity.Attributes["customerid"]).Id;
                        Entity contact = service.Retrieve("contact", customerid, new ColumnSet(true));
                        //Entity contact = service.Retrieve("contact", customerid, new ColumnSet("new_contactclass", "emailaddress1"));
                        string contactClass = contact.FormattedValues["new_contactclass"];
                        string contactEmail = contact.Attributes["emailaddress1"].ToString();
                        string contactName = contact.Attributes["fullname"].ToString();

                        string queueName = "";
                        if (contactClass == "A") { queueName = "Gold"; }
                        else if (contactClass == "B") { queueName = "Silver"; }
                        else if (contactClass == "C") { queueName = "Bronze"; }

                        string fetchXml = @"<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='false'>
                                          <entity name='queue'>
                                            <attribute name='name' />
                                            <attribute name='emailaddress' />
                                            <attribute name='queueid' />
                                            <order attribute='name' descending='false' />
                                            <filter type='and'>
                                              <condition attribute='name' operator='eq' value='{0}' />
                                            </filter>
                                          </entity>
                                        </fetch>";

                        EntityCollection result = service.RetrieveMultiple(new FetchExpression(String.Format(fetchXml, queueName)));
                        Guid queueid = (Guid)result.Entities[0].Attributes["queueid"];

                        //AddToQueueRequest queueRequest = new AddToQueueRequest();
                        //queueRequest.Target = new EntityReference("queue", queueid);
                        //AddToQueueResponse queueResponse = (AddToQueueResponse)service.Execute(queueRequest);

                        Entity queueitem = new Entity("queueitem");
                        service.Create(queueitem);
                        
                    }
                }
                catch (FaultException<OrganizationServiceFault> ex)
                {
                    throw new InvalidPluginExecutionException("An error occurred in MyPlug-in.", ex);
                }
                catch (Exception ex)
                {
                    tracingService.Trace("MyPlugin: {0}", ex.ToString());
                    throw;
                }
            }
        }