string[] trackingNumbers = { "PKG-1001", "PKG-1002", "PKG-1003" };
Action<string> deliveryLogger = message => Console.WriteLine($"[System] Package {message} arrived.");
deliveryLogger += message => Console.WriteLine($"[SMS] Alert for {message}.");
Console.WriteLine("Starting batch processing...");
foreach (var trackingNumber in trackingNumbers)
{
    deliveryLogger(trackingNumber);
}
Console.WriteLine("Batch processing complete.");