public interface IOrderTotalCalculationService { decimal GetShoppingCartShippingTotal(ShoppingCart cart); } public class MyOrderTotalCalculationService : IOrderTotalCalculationService { public decimal GetShoppingCartShippingTotal(ShoppingCart cart) { // Calculate shipping total return 10.00m; } } // Example usage: var cart = new ShoppingCart(); cart.AddItem(new Item("Product 1", 10.00m, 2)); cart.AddItem(new Item("Product 2", 20.00m, 1)); var service = new MyOrderTotalCalculationService(); decimal shippingTotal = service.GetShoppingCartShippingTotal(cart); // Output: 10.00 (assuming MyOrderTotalCalculationService returns a constant value of 10.00 for all shopping carts)Package library: This interface and its implementation could be part of a larger package library related to e-commerce and online shopping. For example, it could be part of a package that includes classes for shopping carts, orders, payment processing, and shipping calculations. This package could be used to build e-commerce websites, mobile apps, or other online shopping platforms.