A high-tech company wants to estimate the mean number of years of college education its employees have completed. A good estimate of the standard deviation for the number of years of college is o = 1.6. How large a sample needs to be taken to estimate the mean number of college years to within + 0.5 years with 95% confidence? Select one: a. 14 O b. 39 O c. 40 O d. 27 O e. 28