With t in years since the start of 2014, worldwide annual extraction of copper is 17.9(1.025)^t million tonnes.
(a) How fast is the annual extraction changing at time t? Give units.
(b) How fast is the annual extraction changing at the start of 2025?
(c) Suppose annual extraction changes at the rate found in part (b) for the five years 2025–2030. By how much does the annual extraction change over this period?
(d) Is your answer to part (c) larger or smaller than the change in annual extraction predicted by the model 17.9(1.025)^t?