Let X be the time needed by the friendly instructor to complete a 100- meter dash, which is assumed to be a normal random variable. The friendly instructor did n : 17 laps, with the following results (in seconds): 21.0 21.1 22.7 19.9 17.4 20.6 16.3 19.3 16.9 17.5 18.9 20.4 19.7 21.8 16.6 20.9 18.0 (a) (10 points) The friendly instructor will participate in Boston Marathan if his average speed is at most 19 seconds. Construct a 90% upper- bound one-sided condence interval. Can you be 90% condent that the instructor will participate in Boston Marathon? (b) How many more laps are needed so that the one-sided estimate is off by at most 0.7 with confidence at least 95%