PT. XYZ produces AA batteries used in remote-controlled toy cars. The mean life of these batteries follows the normal probability distribution with a mean of 35.0 hours and a standard deviation of 5.5 hours. As a part of its quality assurance program, PT. XYZ tests samples of 20 batteries.

What is the probability that the sample mean of useful life is between 34.5 and 36.0 hours? (round answer to 4 decimal places)