I minimized the answers down to 1 and 4, the other two are not correct
Answer:
189 components must be sampled.
Step-by-step explanation:
We have that to find our
level, that is the subtraction of 1 by the confidence interval divided by 2. So:

Now, we have to find z in the Ztable as such z has a pvalue of
.
That is z with a pvalue of
, so Z = 2.575.
Now, find the margin of error M as such

Assume that component lifetimes are normally distributed with population standard deviation of 16 hours.
This means that 
How many components must be sampled so that a 99% confidence interval will have margin of error of 3 hours?
n components must be sampled.
n is found when M = 3. So






Rounding up:
189 components must be sampled.
D-10-2d+7 = 8 + d- 10 -3d
d-2d-10+7 = 8-10 +d -3d
-d-3=-2-2d
-d+2d=3-2
d=1
Final answer: C. d=1
1. Convert percent into decimal (it will help)

2. Convert Decimal to fraction