How to get Organizatoin Service Uri in Plugin in MS Dynamics CRM?

public void Execute(IServiceProvider serviceProvider)
{
	//Extract the tracing service for use in debugging sandboxed plug-ins.
	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"];
		try
		{
			//// Obtain the organization service reference.
			IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
			IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);
			
			//how to get organizationname.crm.dynamics.com/.../Organization.svc
		}
		catch (FaultException<OrganizationServiceFault> ex)
		{
			throw new InvalidPluginExecutionException("An error occurred in the plug-in.", ex);
		}
		catch (Exception ex)
		{
			throw new InvalidPluginExecutionException(String.Format("Handling custom plug-in: {0}", ex.Message), ex);
		}
	}
}