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 velocity at $t = \frac { \pi } { 4 }$ for $\mathbf { r } ( \mathrm { t } ) = 4 \sec ^ { 2 } ( \mathrm { t } ) \mathbf { i } - 5 \tan ( \mathrm { t } ) \mathbf { j } + 10 \mathrm { t } ^ { 2 } \mathbf { k }$

A) $\mathbf { v } \left( \frac { \pi } { 4 } \right) = - 10 \mathbf { j } - 5 \pi \mathbf { k }$
B) $\mathbf { v } \left( \frac { \pi } { 4 } \right) = - 10 \mathbf { j } + 5 \pi \mathbf { k }$
C) $\mathbf { v } \left( \frac { \pi } { 4 } \right) = 16 \mathbf { i } - 10 \mathbf { j } + 5 \pi \mathbf { k }$
D) $\mathbf { v } \left( \frac { \pi } { 4 } \right) = 16 \mathbf { i } + 10 \mathbf { j } - 5 \pi \mathbf { k }$