Sydney and Savannah decide to race in an empty airport. They can both run at speed v on the ground (i.e. stationary surface). In the race, Sydney runs on a moving walkway moving at velocity v/2 to the right. Savannah runs on the ground. They both run from point A to point B a distance L away to the right, and back to point A. Who wins the race? Why? Can you deduce a general rule for this situation?