static void Main(string[] args)
{
Console.WriteLine("Hello World!");
var subject = new Subject();
var greenObserver = new Observer(ConsoleColor.Green);
var redObserver = new Observer(ConsoleColor.Red);
var yellowObserver = new Observer(ConsoleColor.Yellow);
subject.QuantityUpdated += greenObserver.OnUpdateQuantity;
subject.QuantityUpdated += redObserver.OnUpdateQuantity;
subject.QuantityUpdated += yellowObserver.OnUpdateQuantity;
subject.AddToQuantity(12);
subject.AddToQuantity(5);
Console.WriteLine("Enter a key to quit.");
Console.Read();
}