คำนวณเงินเดือนแบบพหุสัณฐาน

using System;
using System.Linq;
abstract class Employee { public abstract decimal Pay(); }
class Salaried(decimal salary) : Employee { public override decimal Pay() => salary; }
class Hourly(decimal rate, int hours) : Employee { public override decimal Pay() => rate * hours; }
class Program
{
    static void Main()
    {
        Employee[] staff = { new Salaried(1000), new Hourly(20, 10) };
        Console.WriteLine(staff.Sum(employee => employee.Pay()));
    }
}