An Object Moves Along a Line in Such a Way $s ( t ) = t ^ { 3 } - 9 t ^ { 2 } + 15 t + 2$

Multiple Choice

An object moves along a line in such a way that its position at time t is $s ( t ) = t ^ { 3 } - 9 t ^ { 2 } + 15 t + 2$ . Find the velocity and acceleration of the object at time t. When is the object stationary?

A) $v ( t ) = 3 t ^ { 2 } - 18 t + 15 ; a ( t ) = 6 t - 18 ; t = 3$
B) $v ( t ) = 3 t ^ { 2 } - 6 t + 15 ; a ( t ) = 6 t - 6 ; \quad t = 1$
C) $v ( t ) = 3 t ^ { 2 } - 18 t + 15 ; a ( t ) = 6 t - 18 ; t = 1$
D) $v ( t ) = 3 t ^ { 2 } - 18 t + 15 ; a ( t ) = 6 t - 18 ; t = 1 \text { and } 5$