1. Air is being let out of a spherical balloon at the rate of 2007 min (a) How fast is the balloon's radius decreasing at the instant the radius is 5 ft? (b) How fast is the surface area decreasing at that instant? m 2. Sand falls from a conveyor belt at the rate of 10 onto the top of a conical pile. The height of the pile is mini always three-eighths of the base diameter. How fast is the height of the pile changing when the pile is 2 m high