Suppose a water bucket is modeled by the frustum of a cone with height I ft and upper and lower radii of I ft and 9 in., respectively, as shown in Figure 3.51. I ft I ft 9 in Figure 3.51 Water bucket If water is leaking from the bottom of the bucket at the rate of 8 in.'/min, at what rate is the water level falling when the depth of water in the bucket is 6 in