public DepositAccount(Customer customer, decimal balance, decimal interestRate)
     : base(customer, balance, interestRate) { }
 public MortgageAccount(Customer customer, decimal money, decimal interestRate)
     : base(customer, money, interestRate) { }
 public BankAccount(Customer customer, decimal balance, decimal interestRate)
 {
     this.Customer = customer;
     this.Balance = balance;
     this.InterestRate = interestRate / 12 / 100;            
 }