The table below shows the incomes and rates of income tax levied on four professionals in an economy. Profession Income per month($) Tax rate % Disposable i...

The table below shows the incomes and rates of income tax levied on four professionals in an economy.
 

Use the above data to answer the questions that follows: 

(a) Calculate the disposable incomes of the four individuals

(b) What system of taxtation was employed?

(c) Give reasons for your answer in 2(b)

(d) With the aid of a diagram, explain the system of taxation employed in 2(b)