If Testing for a 4 Cm or More Difference in Means

Multiple Choice

If testing for a 4 cm or more difference in means between two populations using a two-sample t-test with a = 0.05, what would the approximate (i.e., using a desired power of 0.80) minimum sample size be for each of the samples if the population standard deviation is 16 cm?

A) n = 256
B) n = 266
C) n = 276
D) n = 286