CorrectCode

using System;

namespace Ticket13
{
    public class Teleradio
    {
        public enum TVPack { Эконом, Мини, Универсал }

        public static int AbonentPayment(TVPack chanelNums, bool subscription, bool pensioner)
        {
            double payment = (subscription) ? 300 : 0;

            switch (chanelNums)
            {
                case TVPack.Эконом:
                    payment += 100;
                    break;
                case TVPack.Мини:
                    payment -= 200;
                    break;
                case TVPack.Универсал:
                    payment += 500;
                    break;
                default:
                    break;
            }

            if (pensioner)
                payment *= 0.9;
            if (payment < 0)
                payment = 0;
            return (int)Math.Round(payment);
        }
    }
}