Question 1168670
half-interval is 3 minutes=z(0.995)*sigma/sqrt(n), z=2.576 sigma is 23
so 3=2.576*23/sqrt(n)
sqrt(n)=2.5758*23/3=19.749
n=390 people

note, if one uses 2.576 for z, the answer it 390.03 and that would be rounded up to 391.