Hitting a wall here...is my code on the right track regarding the computed property?

On this Computed Property code challenge, I see that Area is the property to be computed. Every time the SideLength changes, the Area changes, so I understand that the Area property needs to be written as a computed property. I understand further the computed property is the Area property written as a method with an expanded Getter returning how the Area changes whenever the SideLength changes. Is this understanding correct so far?

Second, I am not quite sure how to think about next steps. In the example, there was a code smell caused by the duplicate definitions of the property Location but I am not quite clear where a similar situation is happening here.

Third, are there changes that are supposed to be made to the Polygon class, and why?

Thanks so much, this one has really challenged me and I'm not sure how to proceed.

namespace Treehouse.CodeChallenges
{
    class Square : Polygon
    {
        public double Area 
        { 
            get; 
            {
            return Area.SideLength; 
            }
        }


        public Square(double sideLength) : base(4)
        {
            SideLength = sideLength;
        }
    }
}

namespace Treehouse.CodeChallenges
{
    public class Polygon
    {
        public int NumSides { get; private set; }

        public Polygon(int numSides)
        {
            NumSides = numSides;
        }
    }
}