using System;

​

public class Program

{

    public static void Main()

    {

        IAccount saving = new Savings();

        IAccount chequing = new Chequing();

        IAccount rrsp = new Rrsp();

        saving.Deposit(100);

        saving.Withdraw(10);

        Console.WriteLine(saving.Balance);

        chequing.Deposit(110);

        chequing.Withdraw(30);

        Console.WriteLine(chequing.Balance);

        rrsp.Deposit(200);

        rrsp.Withdraw(220);  // cause an exception --- overdraft

        Console.WriteLine(rrsp.Balance);

    }

    interface IAccount

    {

        decimal Balance { get; }

        void Deposit(decimal amount);

        void Withdraw(decimal amount);

    }

    class Savings : IAccount

    {

        private decimal _balance;

        public void Deposit(decimal amount)

        {

            _balance += amount;

        }

        public void Withdraw(decimal amount)

        {

            _balance -= amount;

        }

        public decimal Balance {get{return _balance;}}

    }

    class  Chequing : IAccount

    {

        private decimal _balance;

        public void Deposit(decimal amount)

        {

            _balance += amount;

        }

        public void Withdraw(decimal amount)

        {

            _balance -= amount;

        }

        public decimal Balance { get { return _balance; } }

    }

    class Rrsp : IAccount

    {

        private decimal _balance;

        public void Deposit(decimal amount)

        {

            _balance += amount;

        }

        public void Withdraw(decimal amount)

        {

            if (_balance - amount < 0)

                throw new Exception(string.Format("Withdrawing {0} would put your account in overdraft.",amount));

            _balance -= amount;

        }

        public decimal Balance { get { return _balance; } }

    }

}