If the requirement of the calculation is as following:

eg: Min 50.00 or 0.20/kg

Since the breakeven point is 250, so if anything is less than 250, then the
charges would be 50.00. However, anything exceed 250 would be based on
0.20*indicated amount. Eg: 0.20*300= 60.00

Kindly advise on how to generate a formula for the above. Thanks in advance.