It Is Known That the Variance of a Population Equals

Essay

It is known that the variance of a population equals 484. A random sample of 81 observations is going to be taken from the population.
A)With a .80 probability, what statement can be made about the size of the margin of error?
B)With a .80 probability, how large of a sample would have to be taken to provide a margin of error of 3 or less?