Find the Derivative of the Following Function $f ( x ) = \log _ { 5 } 8 x$

Multiple Choice

Find the derivative of the following function.
$f ( x ) = \log _ { 5 } 8 x$

A) $\frac { 1 } { x \ln 5 }$
B) $\frac { 5 } { x \ln 8 }$
C) $\frac { 8 } { x \ln 5 }$
D) $\frac { 1 } { 8 x \ln 5 }$
E) none of these