Having recently found sources of oil on their own land, the newly established nation of Brotherton enacted a tariff on imported petroleum in order to raise money for their new government. This trade restriction is an example of a tariff.

revenue tariff

Explanation:

A revenue tariff is a tax levied on imported goods or services whose main purpose is to increase government revenue. It differs from other types of tariffs whose goal is to protect domestic products. E.g. a flat tariff levied on all types of imported goods.

58 stamps is the number she gets each week. So if she went for one week, 58*1=58. 58*2=116 and so on. Because we don't know the exact number of weeks, we say 58w or 58*w because you multiply however many number of weeks she collects.