Problem Solving

hi
Does someone have an idea?

1, The concentration of a certain chemical in a full water tank depends on the depth of the water. At a depth that is x feet below the top of the tank, the concentration is parts per million, where 0 < x < 4. To the nearest 0.1 foot, at what depth is the concentration equal to 6 parts per million?
(A) 2.4 ft
(B) 2.5 ft
(C) 2.8 ft
(D) 3.0 ft
(E) 3.2 ft

absolutely stumped.


or maybe i am not been able to see the question some problem with my browser...
you hv not attached any file with it, right?