Grаvel is being dumped frоm а cоnveyоr belt аnd its coarseness is such that it forms a pile in the shape of a cone whose base radius and height are always equal. When the height of the pile is 3 ft, the height of the pile is increasing at a rate of ft/min. Determine how fast the volume of the gravel pile is increasing at this moment. (The formula for the volume of a cone is