Моля,ако някой може да ми каже къде греша!

using System;

namespace Sandbox
{
    class Sandbox
    {
        static void Main()
        {
            double widthSandBox = double.Parse(Console.ReadLine());
            double lenghtSandBox = double.Parse(Console.ReadLine());
            double priceKiloSand = double.Parse(Console.ReadLine());
            double priceBoard = double.Parse(Console.ReadLine());

            double area = widthSandBox * lenghtSandBox;
            double areaSandBox = (widthSandBox - (0.2 + 0.2)) * (lenghtSandBox - (0.2 + 0.2));
            double areaCurbs = area - areaSandBox;
            double quantitySand = Math.Ceiling(areaSandBox * 20);
            double boards = Math.Ceiling(areaCurbs /(2.2 * 0.2));
            double priceSand = quantitySand * priceKiloSand;
            double priceBoards = boards * priceBoard;
            double result = priceSand + priceBoard;

            Console.WriteLine("{0:f2}", result);

        }
    }
}
Благодаря,предварително!