Answer
a) The gross domestic product was $\$ 16,011.2$ billion.
b) The GDP was $\$13,776$ billion in 2007.
Work Step by Step
(a) $G(13)$ is the output corresponding to the input of $t=13$. So $G(13)$ represents the GDP thirteen years after 2000 . This tells us that, in 2013 , the gross domestic product was $\$ 16,011.2$ billion.
(b) The input to the $G^{-1}$ function is billions of dollars, so its output is a time in years after 2000. Thus, $G^{-1}(13,776)=7$ tells us that, seven years after 2000, the GDP was 13,776 billion dollars. Thus, the GDP was $\$13,776$ billion in 2007.
