11. If $x + 7 y = 29$ is an equation of the line normal to the graph of $f$ at the point $( 1,4 )$, then $f ^ { \prime } ( 1 ) =$ (A) 7 (B) $\frac { 1 } { 7 }$ (C) $- \frac { 1 } { 7 }$ (D) $- \frac { 7 } { 29 }$ (E) - 7
11. If $x + 7 y = 29$ is an equation of the line normal to the graph of $f$ at the point $( 1,4 )$, then $f ^ { \prime } ( 1 ) =$\\
(A) 7\\
(B) $\frac { 1 } { 7 }$\\
(C) $- \frac { 1 } { 7 }$\\
(D) $- \frac { 7 } { 29 }$\\
(E) - 7\\