7.19 Twenty people in one large metropolitan area were asked to record the time (in minutes) that it takes them to drive to work. These times were as follows: 30 42 35 40 45 22 32 15 41 45 28 32 45 27 47 50 30 25 46 25 a. Calculate the standard error. b. Find toa/ for a 95% confidence interval for the true population mean. c. Calculate the width for a 95% confidence interval for the population mean time spent driving to work