create start, pause, resume, stop functions for the Countdown clock

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Countdown
{
    class Program
    {
        static void Main(string[] args)
        {
            Countdown countdown = new Countdown();
            countdown.Start();
            countdown.Pause();
            countdown.Resume();
            countdown.Stop();
            Console.ReadLine();
        }
    }
}