A mixture of silver and copper alloy weighs 128 pounds and contains 12 pounds of silver. How many pounds of silver must be added in order that 8 pounds of the resulting alloy contain 1 pound of silver?

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