(Do not understand how to do this problem at all~Anything helps!)

A population of light bulbs has average lifetime of 600 hours and a standard deviation of 100 hours. Assume the population follows a normal distribution.

A) If you bought a four-pack of bulbs from this population, what is the probability that the average lifetime for the four bulbs is less than 500? Consider the four pack to be sample of n=4.

B) Suppose you bought a 16-paco of bulbs from this population. What is the probability that the average lifetime for the 16 bulbs is less than 500 hours? Consider the 16-pack to be your sample of n=16.