simple delegate

using System;

namespace test
{
    delegate int DiscountDelegate(); 

    class Program
    {
        static void Main(string[] args)
        {
            new ShoppingCart().Process(new DiscountDelegate(Calculator.Calculate));
        }
    }

    class ShoppingCart
    {
        public void Process(DiscountDelegate discount)
        {
            int magicDiscount = discount();
            // ...
        }
    }

    class Calculator
    {
        public static int Calculate()
        {
            int discount = 0;
            if (DateTime.Now.Hour < 12)
            {
                discount = 5;
            }
            else if (DateTime.Now.Hour < 20)
            {
                discount = 10;
            }
            else
            {
                discount = 15;
            }
            return discount;
        }
    } 

}