2. Two mechanics are being compared by a potential customer. The time to complete an oil change at each location on a Thursday is listed for one day. Mechanics A+ #1 Mechanics Time (minutes) Frequency Time (minutes) Frequency 0 - 10 0 0 - 10 1 10 - 20 10 10 - 20 1 20 - 30 7 20 - 30 6 30 - 40 12 30 - 40 18 40 - 50 3 40 - 50 20 50 - 60 5 50 - 60 4 a. Using the midpoints of each interval and the frequencies, find the mean and standard deviation. b. Find the z-scores for 30 min for each mechanic