static void Main(string[] args)
{
StockController controller = new StockController();
TimeSpan workDay = new TimeSpan(0, 0, 2);//2 secs per day
Task t1 = Task.Run(() => new SalesPerson("Sahil").Work(controller, workDay));
Task t2 = Task.Run(() => new SalesPerson("Peter").Work(controller, workDay));
Task t3 = Task.Run(() => new SalesPerson("Juliette").Work(controller, workDay));
Task t4 = Task.Run(() => new SalesPerson("Xavier").Work(controller, workDay));
Task.WaitAll(t1, t2, t3, t4);
controller.DisplayStatus();
}