It is known that cellular phone batteries produced by a certain factory have lifetimes that follow a normal distribution. The average lifetime of the batteries is known to be 2.4 years with a standard...

It is known that cellular phone batteries produced by a certain factory have lifetimes that follow a normal distribution. The average lifetime of the batteries is known to be 2.4 years with a standard deviation of 0.32 years. A random sample of size 16 is to be taken.

a.) What is the probability that a random sample size of 16 will have a sample mean greater than 2.5 years?

b.) What is the probability that a random sample of size 16 will have a mean less than 2.2 years?