Scott,
Since the laser beam takes 29 960.72 s to travel to Neptune and back it takes half that time, 14 980.36 s, to travel from the Earth to Neptune. The laser beam travels 299 792.5 km every second and hence in the 14 980.36 seconds it takes to get to neptune it has travelled
299 792.5 14 980.36 km
Penny
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