8. Norma LeDist is chief engineer for Brightwell Electric, manufacturer of light bulbs. Norma knows that her population of light bulbs is normally dis-tributed with mean 1000 hours and standard deviation 100 hours. What values of z correspond to these lifetimes? (a) 1200 hours (b) 900 hours (c) 1010 hours (d) 1000 hours (e) 895 hours 9. (Exercise 8 continued) In Norma's population, what are the lifetimes of bulbs with these z scores? (a) 1 (b) -2 (c) 1.38 (d) -.2 (e) 0 10. (Exercise 8 continued) (a) What percentage of bulbs have a lifetime shorter than 800 hours? Use the steps of Section 6.4. (b) What percentage of bulbs have a lifetime shorter than 1155 hours? Use the steps of Section 6.4. (c) What percentage of bulbs have a lifetime between 800 and 1155 hours? Use the steps of Section 6.4. Note - all calcuations must be done by hand, using only a calculator