In a time-use study, 40 randomly selected managers were found to spend a mean of 3.14 h each day on paperwork. The population standard deviation is known to be about 1.43 h. Construct the 90 % confidence interval for the mean time spent on paperwork by all managers. Round the z-value to 3 decimal places and the confidence interval values to 2 decimal places. For part (a), use a positive z-value. (a) What is the critical z-value that will need to be used to calculate the confidence interval? (b) What is the 90% confidence interval? CH &lt