Write a computed property named Area that returns the area of the square.

namespace Treehouse.CodeChallenges
{
    class Square : Polygon
    {
        public double SideLength { get; private set; }

        public Square(double sideLength) : base(4)
        {
            SideLength = sideLength;
        }
        private double _area;
        public double Area
        {
        get 
        {
        return _area;
        }
        private set
        {
        _area = SideLength * SideLength;
        }
        }
    }
}

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

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