Find the Average Rate of Change of the Function $f$ Between the Points Given

Multiple Choice

Find the average rate of change of the function $f$ between the points given. $f ( x ) = \frac { 1 } { x - 3 } ; x = 2 , x = 7$

A) $1 / 4$
B) $1 / 5$
C) $- 1 / 5$
D) $- 4$
E) $- 1$