AA128 挺难CRACK的

cournot

128. The following appeared as part of an article in a weekly newsmagazine.

“The country of Oleum can best solve the problem of its balance of
   trade deficit
   by further increasing the tax on its major import, crude oil. After Oleum increased the tax on imported crude oil four months ago, consumption of gasoline declined by 20 percent. Therefore, by imposing a second and significantly higher tax increase next year, Oleum will dramatically decrease its balance of trade deficit.” 

这个og11的新题目挺难的，想不出来怎么crack，请大家出出主意。