7. An object moves along a horizontal line in a way that its position is described by the function s(t) = g3 4t2 + 121 _6, 0 S t S 8, where sis in metres and t is in seconds. [6] a) At what time(s) does the object stop moving? b) At what time(s) does the object have an acceleration of zero? c) Use your previous answers to determine during which time intervals the object is speeding up and slowing down. (Consider setting up a table for this analysis.)