An unidentified flying object (UFO) is observed to travel a total distance of 40000 m, starting and ending at rest, over a duration of 1.72 s. Assuming the UFO accelerated at a constant rate to the midpoint of its journey and then decelerated at a constant rate the rest of the way, what was the magnitude of its acceleration? Express your answer in g s, where 1 g = 9.81 m/s^2.