Lydia proposes to send an interstellar probe off in stages. The first stage, traveling radially outward at 0.500 c relative to Earth, will send off a second stage traveling in the same direction as the first stage at a speed of 0.500 c relative to the first stage. Finally, the second stage will send off a third stage traveling in the same direction at 0.500 c relative to the second stage. Relative to Earth, the speed of the third stage will have a magnitude of?