None of the offered choices is correct.
f(3) = 0.02·2³ = 0.02·8 = 0.16
f(8) = 0.02·2⁸ = 0.02·256 = 5.12
Then the average rate of change is
... (f(8) - f(3))/(8 - 3) = (5.12 -0.16)/5 = 4.96/5 = 0.992
I think this question is a part of another question; you can have any ratio that can add up to 114 cm.
This is pretty much asking "what squared it 0.09". The answer is 0.3, as 0.3 to the power of 2 is 0.09