How to Work out a price per Kilo.

Hi
I hope you can help me. I have weight bands to calculate for delivery purposes and could do with your help.

Less than 20 Kg the charge is £6.00

Over 20 Kg and under 100 Kg £6.00 plus £00.20 per Kg

Over 100 Kg £6.00 plus £00.22 per Kg.

All my figures are in column A

Any help with a formula would be appreciated.