A fleet of delivery trucks operates by making use of the energy stored in a rotating flywheel. The trucks are “charged up” before leaving by using an electric motor to get the flywheel up to its top speed of 5500 revolutions per minute. If one such flywheel is a solid cylinder of mass 700 kg and a diameter of 2.1 m, how long can the truck operate before returning to base for recharging if its average power requirement is 8.0 kilowatts?