The Position Function of a Particle Is Given By $\mathbf { r } ( t ) = \left\langle 5 t ^ { 2 } , 5 t , 5 t ^ { 2 } - 100 t \right\rangle$

Multiple Choice

The position function of a particle is given by $\mathbf { r } ( t ) = \left\langle 5 t ^ { 2 } , 5 t , 5 t ^ { 2 } - 100 t \right\rangle$ When is the speed a minimum?

A) $$t = 5$$
B) $t = 30$
C) $t = 20$
D) $t = 0$
E) $t = 10$