If I am on a train (hypothetically) moving at the speed of light (c) and I start running at a speed of 5 km/hr in the same direction as the train, am I now moving at a speed of c + 5 km/hr? If I am in a subway train moving at the speed of light, and I start running 5 km/hr in the same direction in the train, am I running c+5 km/hr?