Answer: 461
Explanation:
Formula to find the sample size is given by :-
, where n is the sample size ,
is the population standard deviation and
is the two tailed test value of z for significance level (
).
Given :
Margin of error : 3 pounds
Confidence level = 99%
Significance level :

Critical value :

Then, the required minimum sample size would be :-

Hence, the required minimum sample size = 461