Atoms are the smallest unit of matter.
There your answer!
Answer:
9.248 <
< 9.253 mm
Explanation:
Given data:
standard deviation = 0.021 mm
sample mean = 9.251 mm
total sample = 409 m
confidence interval level = 95%
mean diameter of entire batch 
where
- sample mean = 9.251 mm
z = critical value
plugginf all value in the above relation to get the mean diameter

9.248 <
< 9.253 mm