store customer information in a list Customer. first name, last name, zip code, date of birth in the mailer class

class Customer {
  private string _firstName;
  private string _lastName;
  private string _zipCode;
  private DateTime _dateOfBirth;
  
  public Customer(string firstName, string lastName, string zipCode, DateTime dateOfBirth) {
    _firstName = firstName;
    _lastName = lastName;
    _zipCode = zipCode;
    _dateOfBirth = dateOfBirth;
  }
  
  public string FirstName {
    get {
      return _firstName;
    }
  }
  
  public string LastName {
    get {
      return _lastName;
    }
  }
  
  public string ZipCode {
    get {
      return _zipCode;
    }
  }
  
  public DateTime DateOfBirth {
    get {
      return _dateOfBirth;
    }
  }
}

class Mailer {
  List<Customer> customers;
  
  public Mailer() {
    customers = new List<Customer>();