3. A particle moves along a straight horizontal track such that its displacement, \(s\) metres, from a fixed point \(O\) on the line after \(t\) seconds is given by
$$s = 2 t ^ { 3 } - 13 t ^ { 2 } + 20 t$$
- Find the values of \(t\) for which the particle is at \(O\).
- Find the values of \(t\) at which the particle comes instantaneously to rest.