static void Main(string[] args)
{
MotorBike myBike = new MotorBike(new GasEngine(100));
myBike.SetSpeed(90);
Console.WriteLine("Current speed is: " + myBike.CurrentSpeed().ToString());
myBike.RunAtHalfSpeed();
Console.WriteLine("Current speed is: " + myBike.CurrentSpeed().ToString());
Console.ReadLine();
}