A random sample of 400 incomes of unionized transit workers was taken in order to estimate the mean household income and the percentage of incomes that exceed $80,000. The results of this random sample yields the following results:

1. Sample Mean = $40,000.
2. Sample Standard Deviation = $7,500
3. The number of incomes that exceed $80,000 is 60.

A 95% confidence interval for the percentage of incomes that exceed $80,000 in

the population of all transit workers is:

(11.5 , 18.5)

(10.6 , 19.4)

(13.8 , 16.2)

(9.3 , 20.7)

(12.7 , 18.3)