I tried adding these up while looking at the z-values but it's so confusing and I keep making mistakes.

\fPower+, produces AA batteries used in remote-controlled toy ca rs. The mean life of these batteries follows the normal probability distribution with a mean of 20 hours and a standard deviation of 5 hours. As a part of its testing program, Power? tests samples of 25 batteries. Use Appendix 3.1 for the zvalues. a. What can you say about the shape of the distribution of sample mean? Shape of the distribution is b. What is the standard error of the distribution of the sample mean? [Round the nal answer to 4 decimal places.) Standard error c. What proportion of the samples will have a mean useful life of more than 21 hours? {Round the nal answer to 4 decimal places.) Probability d. What proportion ofthe sample will have a mean useful life greater than 19.5 hours? (Round the final answer to 4 decimal places.) Probability e. What proportion of the sample will have a mean useful life between 19.5 and 2'1 hours? {Round the final answer to 4 decimal places.) Probability