A factory supervisor is concerned that the time it takes workers to figure out an important production task (measured in seconds) is too erratic and adversely affects expected profits. The supervisor proceeds by randomly sampling 5 individuals per hour for a period of 10 hours. The sample mean and range for each hour are below.

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Hour X R

1 18.4 25

2 16.9 27

3 23.0 30

4 21.2 23

5 21.0 24

6 24.0 25

7 19.3 12

8 15.8 14

9 20.0 13

10 23.0 11

It also decides that lower and upper specification limit for the critical-to-quality variable should be 10 and 30 seconds.

suppose the supervisor constructs anchart to see if the process is in-control. What is the center line of the chart, as well as the upper and lower lines?

Thank you for any help you can provide.