The thread of a car tire is initially 0.5 cm thick. The tire is safe to drive on as long as it has at least 0.2 cm of tread. Under normal driving conditions this tire is guaranteed 50,000km. Assuming that the guarantee has been computed so that only 1% of tires will actually have to be replaced under the guarantee( ie, will fail within 50,000 km) estimate how much tread wears off of the tire per revolution. Assuming the diameter of the tire is 1 metre.