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 35.0 hours and a standard deviation of 5.5 hours. As a part of its quality assurance program, Power +, Inc. tests samples of 25 batteries This has a normal distribution. The standard error is 1.1.

a. What proportion of the sample will have a mean useful life of more than 36 hours?
b. What proportion of the sample will have a mean useful life greater than 34.5 hours?
c. What is the probability that the sampling error would be less than or more than 1 hour?