The function \small{s(t)} describes the position of a particle moving along a coordinate line,
where \small{s} is in feet and \small{t} is in seconds.
\small{s(t) = t^{4}-18t^{2}+81, \qquad t \ge 0}
If appropriate, enter answers in radical form. Use ** inf ** to represent \small{\infty} .

(a) Find the velocity and acceleration functions.

(b) Find the position, velocity, speed, and acceleration at

Position (ft): | |

Velocity (ft/sec): | |

Speed (ft/sec): | |

Acceleration (ft/sec |

(c) At what times is the particle stopped? Enter as a comma-separated list.

= |

(d) When is the particle speeding up? Slowing down? Enter using interval notation.

You can earn partial credit on this problem.