Let $f ( x , y ) = e ^ { x y } + 2 x ^ { 2 } y ^ { 2 }$

Multiple Choice

Let $f ( x , y ) = e ^ { x y } + 2 x ^ { 2 } y ^ { 2 }$ . Then the directional derivative of f at (0,1) in the direction of the unit vector $\mathbf { U }$ which is parallel to $\mathbf { v } = - 5 \mathbf { i } + 12 \mathbf { j }$ is

A) $\frac { 5 } { 12 }$
B) $- \frac { 5 } { 12 }$
C) $\frac { 5 } { 13 }$
D) $- \frac { 5 } { 13 }$
E) $- \frac { 7 } { 13 }$