public static void Main(string[] args)
{
Cart cart = new Cart();
cart.AddItem(new Product(12.99, ProductType.BusinessCard));
cart.AddItem(new Product(12.99, ProductType.BusinessCard));
cart.AddItem(new Product(12.99, ProductType.BusinessCard));
cart.AddItem(new CouponAll(25));
cart.AddItem(new Product(24.99, ProductType.TShirt));
cart.AddItem(new CouponNext(10));
cart.AddItem(new CouponNextType(15, ProductType.BackPack));
cart.AddItem(new Product(24.99, ProductType.TShirt));
cart.AddItem(new Product(34.99, ProductType.BackPack));
Console.WriteLine("TotalPrice: ${0}", cart.TotalPrice());
}