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.
- $f ( x , y , z ) = \ln \left( x ^ { 2 } + 9 y ^ { 2 } - 7 z ^ { 2 } \right) , \quad P _ { 0 } ( 9,9,9 ) , \quad \mathbf { u } = 3 \mathbf { i } + 4 \mathbf { j }$

A) $\frac { 26 } { 15 }$
B) $\frac { 13 } { 15 }$
C) $\frac { 52 } { 45 }$
D) $\frac { 26 } { 45 }$