A survey of 80 randomly selected large Canadian companies asked them to report the annual income of their presidents. The data is shown below. a. Based on the sample, what is the point estimate for the mean income of presidents of large Canadian companies? b. Assuming that the incomes of presidents of large Canadian companies have a standard deviation of $200,000, determine the margin of error for the 95% level of confidence. c. Assuming that the standard deviation of the incomes of presidents of large Canadian companies is unknown, determine the margin of error for the 95% level of confidence. d. Explain why your answers in parts b and c are different. e. Compute the 95% confidence interval for the annual income of presidents of large Canadian companies, assuming the population standard deviation is unknown. from: to: f. Based on your answers in BOTH parts a and e, explain what the sample indicates about the population