Write a C# Sharp program to compute the sum of the three given integers. However, if any of the values is in the range 10..20 inclusive then that value counts as 0, except 13 and 17

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace exercises
{
   class Program
    {       
        static void Main(string[] args)
        {
            Console.WriteLine(test(4, 5, 7));
            Console.WriteLine(test(7, 4, 12));
            Console.WriteLine(test(10, 13, 12));
            Console.WriteLine(test(17, 12, 18));
            Console.ReadLine();
        }   
       public static int test(int x, int y, int z)
        {
            return Program.fix_num(x) + Program.fix_num(y) + Program.fix_num(z);
        }
        private static int fix_num(int n)
        {
            return (n < 13 && n > 9) || (n > 17 && n < 21) ? 0 : n;
        }
    }
}