Space Find the Speed $s ( t )$ Of the Object

Multiple Choice

$\text { The position vector } \mathbf { r } ( t ) = 8 t \mathbf { i } + + 4 t \mathbf { j } + 5 t \mathbf { k } \text { describes the path of an object moving in }$ space. Find the speed $s ( t )$ of the object.

A) $s ( t ) = 1 / 73$
B) $s ( t ) = 105$
C) $s ( t ) = 1 / 105$
D) $s ( t ) = 1 / 85$
E) $s ( t ) = 17$