sampling distributions and estimators

Suppose that each of 2 statisticians A and B independently takes a random sample of 20 observations from a normal distribution for which the mean mu is unknown and the known value of the variance is 4. suppose also that statistician A finds the sample variance in his random sample to be 3.8. and statistician B finds the sample variance in her random sample to be 9.4. For which random sample is the sample mean likely to be closer to the unknown value of mu??

Any hints or explanations would be greatly appreciated. Do I need to compare z scores maybe?