using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

​

        //Create a list of products

        var products = new List<Product>();

        products.Add(new Product { Name = "PS4", Quantity = 3, Price = 399.99m });

        products.Add(new Product { Name = "Xbox One", Quantity = 10, Price = 399.99m });

        products.Add(new Product { Name = "Wii U", Quantity = 5, Price = 299.99m });

        //Calculate total (qty * price)

        var total = products.Aggregate(0m , (current, p) => current + p.Quantity * p.Price);

        Console.WriteLine(total);

    }

    //Define Product Class

    public class Product {

        public string Name {get; set; } 

        public int Quantity {get; set; }

        public decimal Price {get; set; }

    }

}