using System;

public class Program

{

    class Shape {

      public void setWidth(int w) {

         width = w;

      }

      public void setHeight(int h) {

         height = h;

      }

      protected int width;

      protected int height;

   }

​

   // Base class PaintCost

   public interface PaintCost {

      int getCost(int area);

   }

   // Derived class

   class Rectangle : Shape, PaintCost {

      public int getArea() {

         return (width * height);

      }

      public int getCost(int area) {

         return area * 70;

      }

   }

    public static void Main()

    {

        Rectangle Rect = new Rectangle();

         int area;

         Rect.setWidth(5);

         Rect.setHeight(7);

         area = Rect.getArea();

         // Print the area of the object.

         Console.WriteLine("Total area: {0}",  Rect.getArea());

         Console.WriteLine("Total paint cost: ${0}" , Rect.getCost(area));

    }

}