3.[10 marks] Asample survey of 54 discount brokers showed that the meanprice charged for a
trade of 100shares at $50 per share was $33.77 and a sample standard deviationof $15.
a.   [3] Develop a 95% confidence interval forthe mean price charged by discount brokers for a trade of 100shares at $50 per share.
b.   [2]Explain, in context, what the interval you found tellsyou.
c.    [3]What sample size would be necessary to achieve a margin oferror of $2? Assume a
confidencelevel of 95%.
d.   [2]Three years ago the mean price charged for a trade of 100shares at $50 per share was
$39.25. Hasthe price dropped significantly? Justify.
