Gdp of a developing country a developing countrys gross

Question

Question: GDP OF A DEVELOPING COUNTRY A developing country's gross domestic product (GDP) from 2000 to 2008 is approximated by the function

G(t) = -0.2t³ + 2.4t² + 60              (0 ≤ t ≤ 8)

Where G(t) is measured in billions of dollars and t 0 corresponds to 2000. Show that the growth rate of the country's GDP was maximal in 2004.