Answer:
12 units per second (Answer C)
Step-by-step explanation:
The "average rate of change of a function on an interval" is essentially the following ratio:
change in function over the interval
-----------------------------------------------------
time interval
Here, the time interval is [1, 3] and the corresponding change in the function is found by subtracting f(1) from f(3):
27 - 3
average rate of change: ------------- = 24/2 = 12 units per second
3 - 1
