Suppose There Are Three Power-Generating Plants, Each of Which Has

Multiple Choice

Suppose there are three power-generating plants, each of which has access to 5 different production processes. The table below summarizes the cost of each production process and the corresponding number of tons of smoke emitted each.  
Suppose the government decides to impose a tax on each ton of smoke emitted. What would be the lowest tax, in whole dollars, that would reduce emissions to 6 tons per day?

A) $21 per ton
B) $26 per ton
C) $36 per ton
D) $41 per ton