Find the Average Rate of Change for the Function Over $y=x^{2}+6 x$

Multiple Choice

Find the average rate of change for the function over the given interval.
- $y=x^{2}+6 x$ between $x=7$ and $x=9$

A) $\frac{135}{2}$
B) 15
C) $\frac{44}{9}$
D) 22