A cyclist rides from point A to point B along a straight road and immediately returns to A along the same path, taking equal time for each half of the journey. Which statement correctly describes her average speed vavg and average velocity vˉ for the complete trip?
(a) Both vavg and vˉ are zero.
(b) vavg is zero, while vˉ is positive towards B.
(c) vavg is positive, while vˉ is zero.
(d) vavg is positive, while vˉ is negative towards A.