The Grinch has designed a vacuum that will suck up all the toys in Whoville after Santa delivers them in his new non-aerodynamic sleigh after climbing in the second floor windows. His vacuum, shaped like a right cone with a base of 1000 meters and height of 5000 meters. If the vacuum sucks up toys at the rate of 10,000 cubic meters/second (it’s a good vacuum), what is the change in radius over time when the vacuum is half filled (half of height)?