The Position Vector of a Particle Is R(t) $t = \frac { \pi } { 4 }$

Multiple Choice

The position vector of a particle is r(t) . Find the requested vector.
-The acceleration at $t = \frac { \pi } { 4 }$ for $r ( t ) = ( 2 \sin 2 t ) \mathbf { i } - ( 2 \cos 2 t ) \mathbf { j } + ( 5 \csc 2 t ) \mathbf { k }$

A) $a \left( \frac { \pi } { 4 } \right) = 8 i + 20 k$
B) $a \left( \frac { \pi } { 4 } \right) = - 8 i + 20 k$
C) $\left( \frac { \pi } { 4 } \right) = - 8 \mathbf { i } - 20 \mathbf { k }$
D) $a \left( \frac { \pi } { 4 } \right) = 8 \mathbf { j } + 20 \mathbf { k }$