Answer:
We need a sample size of at least 650
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
.
So it is z with a pvalue of
, so 
Now, find the margin of error M as such

In which
is the standard deviation of the population and n is the size of the sample.
In this problem:
We need a sample of size at least n
n is found when 
So






Rounding up
We need a sample size of at least 650
10*8000= 80,000
An easy way to multiply by 10 is to shift the decimal place over by 1 place value and add a 0 right before it.
I could help but i dont see the question here