Answer:
The smallest sample size required to obtain the desired margin of error is 44.
Explanation:
I think there was a small typing error, we have that
is the standard deviation of these weighs.
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

Which of these is the smallest approximate sample size required to obtain the desired margin of error?
This sample size is n.
n is found when

So



Simplifying by 15



Rounding up
The smallest sample size required to obtain the desired margin of error is 44.