A manufacturer of cream filled donuts wants to make sure that its automatic filling process is on target. Based on a sample of 25 donuts the mean weight of cream filling is estimated to be 15 grams with a standard deviation of 1.5 grams. However, the quality control inspectors wish to estimate the mean weight of cream filling more accurately so that they can be 99% confident that it is within 0.25 grams of the true mean. How many donuts should they sample?

A.

543

B.

410

C.

212

D.

239