In a certain country, income tax $T$ is assessed according to the following function of income $x$ :
$T(x)=\left\{\begin{array}{ll}0 & \text { if } 0 \leq x \leq 10,000 \\ 0.08 x & \text { if } 10,000<x \leq 20,000 \\ 1600+0.15 x & \text { if } 20,000<x\end{array}\right.$
a. Find $T(5,000), T(12,000),$ and $T(25,000)$
b. What do your answers in part (a) represent?