A consumer advocacy group tasted the "on-air" lifetime of a random sample of204cell phone batteries. The mean lifetime was 3 hours with a standard deviation of 0.1 hours. The lifetimes are approximately bell-shaped.

a) Approximately whatpercentage of the batteries have lifetime between 2.8 hours and 3.2 hours?

b) Estimate thenumberof batteries with lifetime between 2.8 hours and 3.2 hours. Round answer to two decimal places