How to calculate the express freight?

Express freight calculation formula: (total weight-first weight) * continued weight price+first weight price = express freight.

Renewal price: 2~5 yuan/kg in the province and 5~8 yuan/kg outside the province; First price: the general first price is 1 kg, and the first price of parts in the province is about 10 yuan; The price of parts from other places in the province 12~ 15 yuan.