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 3+(4/sq root(5-x) )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

Vivek.

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