private static void Billing(IPercentageDiscount percentageDiscount) { var billingService = new BillingService(percentageDiscount, new BillDiscount()); billingService.AddItem(new OtherItem { Name = "Laptop", Price = 50000 }); billingService.AddItem(new OtherItem { Name = "Mobile", Price = 20000 }); billingService.AddItem(new GroceryItem { Name = "Rice", Price = 1000 }); Console.WriteLine(billingService.PrintBill()); }