Answer:
The minimum sample size required to create the specified confidence interval is 2229.
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.
What is the minimum sample size required to create the specified confidence interval
This is n when 





Rounding up
The minimum sample size required to create the specified confidence interval is 2229.
Depends on the fraction to determine your answer
-12/-9=y/-4
cross multiply
-9y=48
divide by 9 on each side
y= -5.33
15÷8=1.875
I would round up to $1.88 /cookie.