Four samples of three observations each have been taken, with actual measurements (in centimeters) shown below.

Construct x bar and R charts, and determine if the production process is under control.

Samples
1	2	3	4
12.3	11.9	12.0	12.1
12.2	12.2	12.2	11.8
12.1	12.2	11.8	11.8