using System;

public class Program

{

    public static void Main()

    {

        Book book = new Book("Joel Jimenez", "C#", 4);

        book.displayRecord();

        Rectangle rec = new Rectangle(5, 9, "Rectangle");

        rec.displayShape();

    }

}

​

class Document {

    protected string author;

    private string title;

    public Document(string author, string title) {

        this.author = author;

        this.title = title;

    }

    public string getAuthor() {

        return author;

    }

    public void display() {

        Console.WriteLine("Author: " + getAuthor());

        Console.WriteLine("Title: " + this.title);

    }

}

​

class Book: Document {

    private int edition;

    public Book(String author, string title, int edition): base(author, title) {

        this.edition = edition;

    }

    public int getEdition() {

        return edition;

    }

    public void displayRecord() {

        base.display();

        Console.WriteLine("Edition: " + getEdition());

        Console.WriteLine();

    }

}

​

abstract class Shape {

    private string shape_name;

    public abstract double getArea();

    public string shapeName { get; set;}

}

​

class Rectangle: Shape {

    private int length, width;

    public Rectangle(int l, int w, string shape_name) {

        this.length = l;

        this.width = w;

        this.shapeName = shape_name;

    }

    public override double getArea() {

        return this.length * this.width;

    }

    public void displayShape() {

        Console.WriteLine(this.shapeName);

        Console.WriteLine(getArea());

    }

}

​