6.27 Lifespan of phone batteries Most phones use lithium-ion

(Li-ion) batteries. These batteries have a limited number of charge and discharge cycles, usually falling between 300 and 500. Beyond this lifespan, a battery gradually diminishes below 50% of its original capacity.

a. Suppose the distribution of the number of charge and discharge cycles was normal. What values for the mean and the standard deviation are most likely to meet the assumption of normality of this variable?

b. Based on the mean and the standard deviation calculated in part

a, find the 95th percentile.