Can some one help please??

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?

Asphere has a diameter of 10 in. what is the volume of the sphere?

The difference of three and the reciprocal of a number is equal to the quotient of 20 and the number. find the number.