using System;

​

public abstract class Animal

{

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    public string name;

    private double weight;

    public bool female;

​

}

​

public class Cat : Animal, Pet 

{

    string breed;

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    public override string ToString()

    {

        return ("Cat: a kitty is here.");

    }

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    //  the Interface requires it!

    public void playful()

    {       

        Console.WriteLine("she seems very playful.");

    }

    public static void Main()

    {

        Cat cat1 = new Cat();

        Console.WriteLine(cat1.ToString());

​

        cat1.playful();

​

    }

}

​

public interface Pet

{

    void playful();

}

​