Find the Derivative of the Function at P0 in the Direction

Multiple Choice

Find the derivative of the function at P0 in the direction of u.
- $$f ( x , y , z ) = \tan ^ { - 1 } \frac { 4 x } { 2 y + 4 z } , \quad P _ { 0 } ( - 9,0,0 ) , \quad \mathbf { u } = 12 \mathbf { i } - 3 \mathbf { j } + 4 \mathbf { k }$$

A) $\frac { 2 } { 117 }$
B) $\frac { 1 } { 78 }$
C) $\frac { 1 } { 117 }$
D) $\frac { 5 } { 234 }$