How to calculate multi tier tariff?

Hi,

I was looking for a solution for calculating multi tier tariff as shown below:

For example below, 0-50 units cost 3.50, above 50 up to 100 will cost 3.90, etc. Finally if consumption exceeds 200, total units will be charged rate of 6.10

Kw Amount
0-50 3.50
51-100 3.90
101-150 4.80
151-200 5.20
>200 6.10

Regards,
Jishar