Ima let go of this acount here free points

Rockwell hardness of pins of a certain type is known to have a mean value of 50 and a standard deviation of 1.1. (round your answers to four decimal places.) (a) if the distribution is normal, what is the probability that the sample mean hardness for a random sample of 8 pins is at least 51?

Which one ? is the answer and how to find this answer

The total number of dental clinics total for the last 12 months was recorded