Table 2.7 shows world gold production, G = f(t), as a function of year, t.
(a) Does f'(t) appear to be positive or negative? What does this mean in terms of gold production?
(b) In which time interval does f'(t) appear to be greatest?
(c) Estimate f'(2015). Give units and interpret your answer in terms of gold production.
(d) Use the estimated value of f'(2015) to estimate f(2016) and f(2020), and interpret your answers.

Table 2.7 World gold production t (year) 2011 2012 2013 2014 2015 G (metric tons) 2660 2690 2800 2990 3000