An assembly is formed by fitting a shaft into a bearing. The outside diameters of the shafts are normally distributed with a mean 2.004 cm and standard deviation 0.001 cm. The inside diameters of bearings are normally distributed with a mean 2.010 cm and standard deviation 0.002 cm. Shafts and bearings are randomly selected to form assemblies. What is the probability that the clearance between a shaft and bearing is positive?