Answer:
it's 1.1 I hoped this helped
The company installs 5000 light bulbs with an average of 500 hours for each bulb. The standard deviation of 100 hours and distribution approximated by a normal curve. The percentage of bulbs that can be expected to last the period of time of less than 690 hours is 97.1%. This will make the answer to be C.
For part A, lets write the problem
add

to both sides

we are going to reverse the inequality, to do this we are going to multiply both sides by



divide both sides by


our answer would be

lets go with part b, lets write the problem

subtract

from both sides


divide both sides by


I few simplified it, we would be left with,

I hope this helped!!
- Kiana