What Is the Rate of Change Of $f ( t ) = \frac { 2 t - 7 } { t + 6 }$

What is the rate of change of $f ( t ) = \frac { 2 t - 7 } { t + 6 }$ with respect to t when t = 13?

A) -19
B) 19
C) $\frac { 1 } { 19 }$
D) $- \frac { 1 } { 19 }$