A biology class at Troy high school predicted that the local population of animals double in every 10 years. The population at the beginning of 2012 was estimated to be 40 animals. If $P$ represents population $n$ years after 2012, then which of the following equation represents the classes model of the population over time ?

Question

$\begin{array}{1 1} (a)\; P = 10 +40n \\(b)\; P=40+10n \\(c)\; P = 50(2)^{10n} \\ (d)\; P = 50(2)^{ \large\frac{n}{10}} \end{array}$