A fuel is purified by passing it through a clay pipe. Each foot of the clay pipe removes a fixed percentage of impurities in the fuel. Let f(x) represent the amount of pollutants, in tons, left in the fuel after it had passed through x feet of the clay pipe: f(x) = 10(0.8)x What does the number 0.8 represent? Every foot of the pipe keeps 80% of the pollutant. Every foot of the pipe removes 80% of the pollutant. The original amount of pollutant present in the fuel was 80 tons. The original amount of pollutant present in the fuel was 20 tons.