public static double Calc(Digit a, Digit b)
 {
     if ((a == null) || (b == null))
     {
         throw new ArgumentNullException("arrgs cannot be null");
     }
     else
     {
         var sum = a.Value + b.Value;
         return(sum);
     }
 }
        public static void Main(string[] args)
        {
            Console.WriteLine("----Task 1----");
            Digit a = new Digit();

            a.Value = 10;
            Digit b = new Digit();

            b.Value = 20;
            Console.WriteLine(Program.Calc(a, b));
            Console.WriteLine("----Task 2----");
            StartButton startbutton1 = new StartButton();
            Car         car1         = new Car(startbutton1);

            Console.WriteLine(car1.Start());
            Console.ReadLine();
        }