The life of a particular type of light bulb is normally distributed with a mean of 1000 and a standard deviation of 150 hours. The manufacturer is considering a warranty. a. What proportion of the...

The life of a particular type of light bulb is normally distributed with a mean of 1000 and a standard deviation of 150 hours. The manufacturer is considering a warranty.

a. What proportion of the bulbs have a life of more than 1150 hours?

b. What proportion of the bulbs have a life of between 925 and 1150 hours?

c. If the manufacturer wants to replace no more than 5% of the bulbs under warranty, how many hours should the warranty cover?