Use the Limit Definition to Find the Slope of the Tangent

Multiple Choice

Use the limit definition to find the slope of the tangent line to the graph of $f ( x ) = \sqrt { 4 x + 25 }$ at the point $( 6,7 )$ .

A) $\frac { 2 } { 7 }$
B) $- \frac { 2 } { 7 }$
C) $\frac { 1 } { 7 }$
D) $- \frac { 1 } { 7 }$
E) $\frac { 1 } { 6 }$