Afuel 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 removes 20% 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.