Задача: Стоимость арифметических операций

GetCostOfSumNumbers.cs

using System;
using System.Linq;
using System.Collections.Generic;
					
public class Program
{
	private static int GetCostOfSumNumbers(int[] numbers)
	{
		int result = 0;
		var collection = new List<int>(numbers.OrderBy(n => n));
		while (collection.Count > 1)
		{
			int x = collection[0]; collection.Remove(x);
			int y = collection[0]; collection.Remove(y);

			int res = x + y;
			collection.Add(res);
			collection = collection.OrderBy(n => n).ToList();
			result += (res);
		}

		return result;
	}

	public static void Main()
	{
		Console.WriteLine("UniLecs");
		
		Console.WriteLine(string.Format("Answer = {0}", GetCostOfSumNumbers(new int[] { 1, 2, 3 })));	 // 9
		Console.WriteLine(string.Format("Answer = {0}", GetCostOfSumNumbers(new int[] { 1, 2, 3, 4 }))); // 19		
	}
}