how much pure alchohol must a nurse add to 10cm of a 60% alchohol solution to streghen it to a 90% solution pls pls pls

Gravel is being dumped from a conveyor belt at a rate of 25 ft3/min, and its coarseness is such that it forms a pile in the shape of a cone whose base diameter and height are always equal. how fast is the height of the pile increasing when the pile is 14 ft high? (round your answer to two decimal places.) ft/min