With an initial deposit of $100, the balance in a bank account after t years is f

Question:

With an initial deposit of $100, the balance in a bank account after t years is f (t) = 100(1.08)t dollars.
(a) What are the units of the rate of change of f (t)?
(b) Find the average rate of change over [0, 0.5] and [0, 1].
(c) Estimate the instantaneous rate of change at t = 0.5 by computing the average rate of change over intervals to the left and right of t = 0.5.