Answer:
B
Explanation:
The average rate of change of f(x) in the closed interval [ a, b ] is
![(f(b)-f(a))/(b-a)](https://img.qammunity.org/2021/formulas/mathematics/middle-school/18ms4kih9wr23b7ul4i1oojtgr33aob1uy.png)
Here a = 1 and b = 3
f(b) = f(3) = 27 ← value of y corresponding to x = 3
f(a) = f(1) = 3 ← value of y corresponding to x = 1, thus
average rate of change =
=
= 12 → B