protected Account(Customer customer, decimal balance, double interestRate)
 {
     this.Customer = customer;
     this.Balance = balance;
     this.InterestRate = interestRate;
 }
 public Loan(Customer customer, decimal balance, double interestRate)
     : base(customer, balance, interestRate)
 {
 }
 public Mortgage(Customer customer, decimal balance, double interestRate)
     : base(customer, balance, interestRate)
 {
 }