Kolum Tariff group NAF/kWh
A ≤ 250 0.4761 cents
B >250 ≤ 350 0.5824 cents
C >350 0.6266 cents

I have 3 tariff groups like above.

If the usage for example = 240 till or equals 250 = 240 x 0.4761

If >250 ≤ 350