In an application to estimate the mean number of miles that downtown employees commute to work roundtrip each day, the following information is given:

n: 20

x = 4.33

s= 3.50

Based on the information, the upper limit for a 95% confidence interval estimate for the true population mean is:

a) Nearly 12.0 miles

b) about 5.86 miles

c) About 5.97 miles

d) about 7.83 miles