In the sample survey of 54 discount brokers that showed that the mean price charged for a trade of 100 shares at $50 per share was $33.77 (aaii journal, february 2006). the survey is conducted annually. with the historical data available, assume a known population standard deviation of $15. what the 95% confidence interval estimate of the population mean?

a. ucl = 52.94 lcl = 47.06

b. ucl = 36.71 lcl = 30.83

c. ucl = 50.54 lcl = 49.46

d. ucl = $37.77 lcl = $29.77