Inheritance in c#

using System;

namespace InheritanceApplication

{ 

    class Shape

   {

      public void setWidth(int w)

      {

         width = w;

      }

      public void setHeight(int h)

      {

         height = h;

      }

      protected int width;

      protected int height;

   }

   

   public interface PaintCost

   {

      int getCost(int area);

   }

  

  

   class Rectangle : Shape, PaintCost

   {

      public int getArea()

      {

         return (width * height);

      }

      public int getCost(int area)

      {

         return area * 70;

      }

   }

   class RectangleTester

   {

      static void Main(string[] args)

      {

         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));

         Console.ReadKey();

      }

   }

}