I did 51500/6.8% =3502 and still got it wrong for the minimum tax

Given the following tax structure, Taxpayer Salary Total Tax Mae $12,500 $ 850 Pedro $51,500 ??? a. What is the minimum tax that Pedro should pay to make the tax structure vertically equitable with respect to the amount of tax paid? Minimum tax $ 3,502 b. This would result in what type of tax rate structure? Tax rate structure Regressive