static void Main(string[] args)
        {
            SunTimes times = new SunTimes(DateTime.Now.AddHours(-2), DateTime.Now.AddHours(8));
            Console.WriteLine("Daylight minutes: " + times.DaylightMinutes());

            ShoppingCart cart = new ShoppingCart();
            cart.AddProduct(1400);
            cart.AddProduct(17);
            cart.Checkout();
        }
        static void Main(string[] args)
        {
            SunTimes times = new SunTimes(DateTime.Now.AddHours(-2), DateTime.Now.AddHours(8));

            Console.WriteLine("Daylight minutes: " + times.DaylightMinutes());

            ShoppingCart cart = new ShoppingCart();

            cart.AddProduct(1400);
            cart.AddProduct(17);
            cart.Checkout();
        }
        static void Main(string[] args)
        {
            Rational rational = new Rational(1, 3);
            Rational another = new Rational(1, 2);
            rational.Add(another);
            Console.WriteLine("Sum: " + rational.Numerator + "/" + rational.Denominator);

            ShoppingCart cart = new ShoppingCart();
            cart.AddProduct(1400);
            cart.AddProduct(17);
            cart.Checkout();
        }
        static void Main(string[] args)
        {
            Rational rational = new Rational(1, 3);
            Rational another  = new Rational(1, 2);

            rational.Add(another);
            Console.WriteLine("Sum: " + rational.Numerator + "/" + rational.Denominator);

            ShoppingCart cart = new ShoppingCart();

            cart.AddProduct(1400);
            cart.AddProduct(17);
            cart.Checkout();
        }