C.area()=？

namespace Ex3._9
{
    class Shape
    {
        protected double height;
        protected double width;
        public Shape()
        {
            height = width = 0;
        }
        public Shape(double x)
        {
            height = width = x;
        }
        public Shape(double h, double w)
        {
            height = h;
            width = w;
        }
        public double area()
        {
            return height * width;
        }

    }
    class Triangle : Shape
    {
        public Triangle(double x, double y) : base(x, y) { }
        new public double area()
        {
            return height * width / 2;
        }

    }
    class Trapezia : Shape
    {
        double width2;
        public Trapezia(double w1, double w2, double h) : base(w1, h)
        {
            width2 = w2;
        }
        new public double area()
        {
            return (width + width2) * height /2;
        }
        class Program
        {
            static void Main(string[] args)
            {
                Shape A = new Shape(2, 4);
                Triangle B = new Triangle(1, 2);
                Trapezia C = new Trapezia(2, 3, 4);
                Console.WriteLine("A.area()={0}", A.area());
                Console.WriteLine("B.area()={0}", B.area());
                Console.WriteLine("C.area()={0}", C.area());
                A = B;
                Console.WriteLine("A.area()={0}", A.area());
                A = C;
                Console.WriteLine("A.area()={0}", A.area());
                Console.Read();
            }
        }
    }
}

结果里C.area()=7
为什么不是C.area()=10,（2+3）*4/2=10？

public Trapezia(double w1, double w2, double h) : base(w1, h)
参数列表顺序错了，应该是base(h,w1)