What is the average rate of change for this quadratic function for the interval from x=3 to x=4

ANSWER
A. 27.5
EXPLANATION
The average rate of change of the given quadratic function on the interval;
x=2 to x=4 is the slope of the secant line connecting the points (2,f(2)) and (4,f(4)).
This implies that the average rate of change is
[tex] = \frac{f(4) - f(2)}{4 - 2} [/tex]
From the table,
[tex]f(4) = 64[/tex]
and
f(2)=9.
The average rate of change becomes
[tex] = \frac{64 - 9} {4 - 2} [/tex]
[tex] = \frac{55}{2} = 27.5[/tex]
The correct choice is A.