help me A certain type of automobile battery is known to have a lifespan that is normally distributed, with mean 1100 days and standard deviation 80 days. For how long should these batteries be...

help me

A certain type of automobile battery is
known to have a lifespan that is normally
distributed, with mean 1100 days and
standard deviation 80 days. For how long
should these batteries be guaranteed if the
manufacturer wants to replace only 5% of the
batteries sold because they “died” before the
guarantee expired?