A Factory Is Polluting a River Such That at Every

Multiple Choice

A factory is polluting a river such that at every mile down river from the factory an environmental expert finds 15% less pollutant than at the preceding mile.If the pollutant's concentration is 600 ppm (parts per million) at the factory,what is its concentration 12 miles down river? ​

A) 180 ppm
B) ​90 ppm
C) ​85.35 ppm
D) 705.88 ppm
E) ​100.41 ppm