Power +, Inc. produces AA batteries used in remote-controlled toy cars. The mean life of these batteries follows the normal probability distribution with a mean of 37 hours. hours and a standard deviation of 5.5 hours. As a part of its quality assurance program, Power +, Inc. tests samples of 25 batteries. What proportion of the samples will have a mean useful life of more than 38 hours? What proportion of the sample will have a mean useful life greater than 36.5 hours? What proportion of the sample will have a mean useful life between 36.5 and 38 hours?