Question 1041533
The standard error has to be 20 mg
It is z*s/sqrt (n), since we don't have n, we can't use a t-test.  Also, the number is likely to be quite large.
20=1.645*200/sqrt(n)
multiply both sides by (sqrt(n)); divide both by 20
sqrt(n)=200*1.645/10=32.9
n=32.9^2=1082.41 or 1083 nickels, rounding upward