Given the Following Tax Structure, What Is the Minimum Tax

Essay

Given the following tax structure, what is the minimum tax that would need to be assessed on Lizzy to make the tax progressive with respect to average tax rates? What is the minimum tax that would need to be assessed on Lizzy to make the tax progressive with respect to effective tax rates?
$$\begin{array} { | l | r | r | r | } \hline { \text { Tuxpayer } } & \text { Salary } & { \text { Muni-Band Interest } } & { \text { Total Tax } } \\\hline \text { Mort } & 20,000 & 5,000 & 4,000 \\\hline \text { Lizzy } & 80,000 & 30,000 & ? ? ? \\\hline\end{array}$$