public static void Main(string[] args)
{
IPriceCalculator pc = new PriceCalculator();
List <Item> items = pc.ReadShoppingItems();
List <Offer> offers = pc.ReadOffers();
DisplayItems(items);
DisplayOffers(items, offers);
Console.WriteLine("");
Console.WriteLine("Add items in your cart. Enter Item Id to add in your cart. Press 'E' any time to exit.");
var cart = pc.AddInCart(items);
Console.WriteLine("");
Console.WriteLine("S/N Name Quantity Price");
DisplayCart(cart);
Console.WriteLine();
Console.WriteLine("Your Free Items***");
var freeItems = pc.AddFreeItems(items, cart.ToList(), offers);
DisplayCart(freeItems);
Console.WriteLine();
DisplayPrice(cart);
Console.Read();
}