public Triangle(double height, double width)
        {
            SimpleValidator.CheckNotPositive((decimal)height, "height");
            SimpleValidator.CheckNotPositive((decimal)width, "width");

            this.Height = height;
            this.Width  = width;
        }
        public override decimal CalculateInterest(int periodInMonths)
        {
            SimpleValidator.CheckNotPositive(periodInMonths, "Interest period");

            if (this.Balance > 0M && this.Balance < 1000M)
            {
                return(0);
            }

            return(base.CalculateInterest(periodInMonths));
        }