Upgrade }{Y|TA

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Xml;

namespace HotelAccounting
{
    //создайте класс AccountingModel здесь
    public class AccountingModel : ModelBase
    {
        private double price;

        public double Price
        {
            get { return price; }
            set
            {
                if (value < 0) throw new ArgumentException();
                else
                {
                    price = value;
                    Notify(nameof(Price));
                    Notify(nameof(Total));
                }
            }
        }

        private int nightsCount;

        public int NightsCount
        {
            get { return nightsCount; }
            set
            {
                if (value <= 0) throw new ArgumentException();
                else
                {
                    nightsCount = value;
                    Notify(nameof(NightsCount));
                    Notify(nameof(Total));
                }
            }
        }

        private double discount;

        public double Discount
        {
            get
            {
                return discount;
            }
            set
            {
                if (value > 100) throw new ArgumentException();
                discount = value;
                Notify(nameof(Discount));
                Notify(nameof(Total));
            }
        }

        private double total;

        public double Total
        {
            get { return Price*NightsCount*(1 - Discount/100); }
            set
            {
                if (value <= 0) throw new ArgumentException();
                Discount = 100 - 100*value/(Price*NightsCount);
            }
        }
    }
}