using System;

public class BankAccount {

   protected double interestRate;
   protected string owner;
   protected decimal balance;

   public BankAccount(string o, decimal b, double ir) {
      this.interestRate = ir;
      this.owner = o; 
      this.balance = b;
   }

   public BankAccount(string o, double ir):
     this(o, 0.0M, ir) {
   }

   public virtual decimal Balance {
     get {return balance;}
   }

   public virtual void Withdraw (decimal amount) {
      balance -= amount;
   }

   public virtual void Deposit (decimal amount) {
      balance += amount;
   }

   public virtual void AddInterests() {
      balance += balance * (Decimal)interestRate;
   }    

   public override string ToString() {
      return owner + "'s account holds " +
            + balance + " kroner";
   }
} 


public class CheckAccount: BankAccount {

   // Instance variables are inherited

   public CheckAccount(string o, double ir): 
     base(o, 0.0M, ir) {
   }

   public CheckAccount(string o, decimal b, double ir): 
     base(o, b, ir) {
   }

   // Method Balance is inherited
   // Method Deposit is inherited
   // Method AddInterests is inherited

   public override void Withdraw (decimal amount) {
      base.Withdraw(amount);
      if (amount < balance)
         interestRate = -0.10;
   }

   public override string ToString() {
      return owner + "'s check account holds " +
            + balance + " kroner";
   }
} 

public class SavingsAccount: BankAccount {

   // Instance variables are inherited

   public SavingsAccount(string o, double ir): 
     base(o, 0.0M, ir) {
   }

   public SavingsAccount(string o, decimal b, double ir): 
     base(o, b, ir) {
   }

   // Method Balance is inherited
   // Method Deposit is inherited

   public override void Withdraw (decimal amount) {
      if (amount < balance)
          base.Withdraw(amount);
      else
          throw new Exception("Cannot withdraw");
   }

   public override void AddInterests() {
      balance = balance + balance * (decimal)interestRate 
                        - 100.0M;
   }    

   public override string ToString() {
      return owner + "'s check account holds " +
            + balance + " kroner";
   }
} 

public class LotteryAccount: BankAccount {

   // Instance variables are inherited

   protected static Lottery lottery  = Lottery.Instance(3);

   public LotteryAccount(string o, decimal b): 
     base(o, b, 0.0) {
   }

   // Method Balance is inherited
   // Method Deposit is inherited
   // Method Withdraw is inherited

   public override void AddInterests() {
      int luckyNumber = lottery.DrawLotteryNumber;
      balance = balance + lottery.AmountWon(luckyNumber);
   }    

   public override string ToString() {
      return owner + "'s lottery account holds " +
            + balance + " kroner";
   }
} 

public class Lottery{

  private static Random rdm = new Random(unchecked((int)DateTime.Now.Ticks));

  private int difficulty;
  private readonly int winningNumber;
  private readonly decimal amountWon;
  private static Lottery uniqueInstance = null;

  private Lottery(int difficulty){
    this.difficulty = difficulty;
    this.winningNumber = rdm.Next(difficulty);
    this.amountWon = 500000.00M;
  }

  public static Lottery Instance(int difficulty){
    if (uniqueInstance == null)
      uniqueInstance = new Lottery(difficulty);
    return uniqueInstance;
  }

  public int DrawLotteryNumber{
    get {return rdm.Next(difficulty);}
  }

  public bool IsWinningNumber(int number){
    return number == winningNumber;
  }

  public decimal AmountWon(int luckyNumber){
    decimal res;
    if (IsWinningNumber(luckyNumber))
       res = amountWon;
    else
       res = 0.0M;
    return res;
  }
}

public class AccountClient{

  public static void Main(){
     BankAccount[] accounts = 
      new BankAccount[5]{
        new CheckAccount("Per",1000.0M, 0.03),
        new SavingsAccount("Poul",1000.0M, 0.07),
        new CheckAccount("Kurt",10.0M, 0.02),
        new LotteryAccount("Bent",10500.0M),
        new LotteryAccount("Lone",11500.0M)
      };

    foreach(BankAccount ba in accounts){
       ba.Deposit(1000.0M);  
    }  
 
    accounts[2].Withdraw(1050.0M);  // Kurt's

    foreach(BankAccount ba in accounts){
      ba.AddInterests();  
    }  

    foreach(BankAccount ba in accounts){
      Console.WriteLine("{0}", ba);
    }
  }

}