(1 point) While time t > 0 a particle moves along a straight line. Its position at time t is given by s(t) = 2t3 - 27t + 84t, t0 where s is measured in feet and t in seconds. (A) Use interval notation to indicate the time interval or union of time intervals when the particle is moving forward and backward. Forward: Backward: (2,7) (B) Use interval notation to indicate the time interval(s) when the particle is speeding up and slowing down. Speeding up: Slowing down: ("Speeding up" and "slowing down" refer to changes in speed, the absolute value of velocity.)