GDP of a Country

The gross domestic product (GDP) of a certain country is

f(t) = 0.1t³ + 0.7t² + 2t + 23 (0 t 4)

billion dollars in year t, where t is measured in years with t = 0 corresponding to 2010.

(a)

What was the GDP of the country in 2013?

$ billion

(b)

How fast was the GDP of the country changing in 2013?

$ billion/yr