A conical salt spreader is spreading salt at a rate of 4 cubic feet per minute. The diameter of the base of the cone is 4 feet and the height of the cone is 5 feet. How fast is the height of the salt in the spreader decreasing when the height of the salt in the spreader (measured from the vertex of the cone upward) is 3 feet? Give your answer in feet per minute. (Just give the number. It will be a positive number since we use the word "decreasing".)

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