using System;

​

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Calculate rectangle area 5x7.");

        Console.WriteLine((new Rectangle()).Area(5,7));

        Console.WriteLine("Extend your class to calculate perimeter.");

        //You can't change class Retangle

        //Console.WriteLine((new Rectangle()).Perimeter(5,7));

    }

}

​

public class Rectangle

{

    public int Area(int a,int b)

    {

        return a*b;

    }

}

​

​

​

​