A random sample of 49 lunch customers was taken at a restaurant. The average amount of time the customers in the sample stayed in the restaurant was 33 minutes. From past experience, it is known that the standard deviation equals 10 minutes. With a .99 probability, how large of a sample would have to be taken to provide a margin of error of 2.5 minutes or less?

Select one:

A. 117

B. 107

C. 97

D. 87