Finding it hard to get started on a query I have been given which is about calculating an employees tax.

There are two types of employees, standard and self-employed. The following detials apply

Tax Rates:

Standard PAYE Employee
20% tax free, 20% @ 15% and the rest at 30%

Self-employed PAYE Employee
40% tax free, 20% on the rest

I need to have:
An Employee class
CalculateTax Method makes use of appropriate calculation
Create a Government class which has an array of employees
Extend user so it has a boolean (selfEmployed)
Iterate through array and calculate total tax from self employed and total
tax from standard

any help on this would be greatly appreciated!