The gross annual earnings of a certain company were A(t) = 0.3t + 12t + 21 thousand dollars t years after its formation in 2008.

The gross annual earnings of a certain company were A(t) = 0.3t² + 12t + 21 thousand dollars t years after its formation in 2008. At what percentage rate were the gross annual earnings growing with respect to time in 2012? 18.74% per year20.44% per year19.51% per year17.89% per year