A conical tank (with vertex down) is 12 feet across the top and 18 feet deep. if water is poured into the tank at a rate of 18 cubic feet per minute, find the rate of change of the depth of the water when the water is 10 feet deep. A. 9/40π ft/min B. 9/100π ft/min C. 81/20π ft/min D. 81/50π ft/min
