BIG Corporation produces just about everything but is currently interested in the lifetimes of its batteries, hoping to obtain its share of a market boosted by the popularity of portable CD and MP3 players. To investigate its new line of Ultra batteries, BIG randomly selects 1000 Ultra batteries and finds that they have a mean lifetime of 89 hours, with a standard deviation of 85 hours. Suppose that this mean and standard deviation applies to the population of all Ultra batteries. Complete the following statements about the distribution of lifetimes of all Ultra batteries.

(a) According to Chebyshev's theorem, at least____ of the lifetimes lie between 763.5 hours and 1018.5.

(b) According to Chebyshev's theorem, at least ____ of the lifetimes lie between 721 hours and 1061.

(c) Suppose that the distribution is bell-shaped. According to the empirical rule, approximately ___ of the lifetimes lie between 721 hours and 1061.

(d) Suppose that the distribution is bell-shaped. According to the empirical rule, approximately 99.7% of the lifetimes lie between _____

hours

and

_____hours.

.