Answer:
n = 139
It isnt reasonable for a real world calculation
Explanation:
The error for the true mean is calculated as follows:

the z score for a 95% confidence is 1.96, replacing in the formula above you get:

Solving for n you get that n = 138.3 = 139
According to (Yamane, 1967) for populations bigger than 100,000 you need a sample size of 1,111