In a Manufacturing Process a Machine Produces Bolts

Multiple Choice

In a manufacturing process a machine produces bolts. The lengths of the bolts follow a normal distribution with an average of 3 cm and a variance of 0.03 cm2. If we randomly select three bolts from this process:
-What is the probability the mean length of the bolt is at most 3.1 cm?

A) 0.8413
B) 1
C) 0.7157
D) 0.2843
E) 0.1587