Show work for all three

Exercise 15. Air is being pumped into a spherical balloon at a rate of 100 cm3/s. How fast is the radius of the balloon increasing when the diameter is 500m? [The volume of a sphere of radius r is V = wr3.] Exercise 20. A tracking telescope on the radar station stays focused on the plane as the plane ies horizontally overhead at an altitude of 5 km. If the angle that the telescope makes with the ground is decreasing at a rate of 7r/ 6 rad/ min at the moment when the angle is 7r/ 3, how fast is the plane moving? Exercise 21. A boat is pulled into a dock by a rope attached to the bow of the boat. The rope is pulled at 1 m/s through a pulley on the dock that is 1 m above the boat. At what rate is the boat approaching the dock when it is 8 m from the dock