A quality control inspector will measure the salt content (in milligrams) in a random sample of bags of potato chips from an hour of production. Which of the following would result in the smallest margin of error in estimating the mean salt content m?

(a) 90% confidence; n = 25

(b) 90% confidence; n = 50

(c) 95% confidence; n = 25

(d) 95% confidence; n = 50

(e) n = 100 at any confidence level