Which of the following statements are correct regarding a flat tax? $($Check all that apply.$)$

A flat tax is a single tax rate applied to an entire tax base.

With a flat tax, different portions of a tax base may be taxed at different rates.

With a flat tax, higher income brackets will be assessed at a higher tax rate than lower income brackets.

The term graduated tax has the same meaning as flat tax.

The term proportiofl tax has the same meaning as flat tax.