3. A spherical balloon is being inflated at a rate of 3 x m /min. Twelve minutes after the inflation first begins, what is the rate of increase of the diameter of the balloon with respect to time? (0.16 m/min) 4. A spherical balloon is inflated such that its radius is increasing at the rate of 1 cm/min. Find the rate of increase of volume when a) when the diameter D is 2 m. (40 000 7 cm /min) b) when the surface area S is 324 x cm (324 cm /min) 5. A weather balloon with radius 9 m springs a leak, losing air at 171 x m /min. Find the rate of decrease of the radius after 4 min. (1.19 m/min) 6. A weather balloon rises through the air at a rate of 500 m/min. Every 1000 m the decrease of air pressure outside the valloon causes its radius to increase by 8 cm. How rapidly is the volume increasing at the instant its radius is 90 cm? (0. 1296 x m /min)