The table below shows a recent graduate's credit card balance each month after graduation.

$\backslash$table$[[$Month$,1,2,3],[$Debt $($$$),620\mathrm{.}00,761\mathrm{.}88,899\mathrm{.}80]]$

a$)$ Look at the graph on your calculator. Based on this graph, what type of equation should represent this situation? Explain your answer.

b$)$ Use your calculator to find the equation that you feel best fits this data. What is the equation?

c$)$ Based on this equation, what is the predicted amount of debt for month $9$ after graduation?