A runner completes two segments: first she jogs 400 m due east, then immediately 400 m due west, taking a total of 200 s. Which statement about her motion is true?
(a) Her displacement is 0m and her average velocity is 4.0m/s east.
(b) Her displacement is 0m and her average speed is 4.0m/s.
(c) Her displacement is 400m east and her average velocity is 4.0m/s east.
(d) Her displacement is 0m and her average speed is 2.0m/s.