Auto pistons are produced in a forging process, and the average diameter is a critical factor that must be controlled. From samples collected on 5 different days (one sample each day, each sample contains 10 pistons), the mean and the range of the diameters have been measured as follows:

Day	Mean (mm)	Range (mm)
1	154.9	4.4
2	153.2	4.8
3	151.6	4.3
4	153.5	4.8
5	156.6	4.5

Assuming 99.73% as the confidence level, choose the right control chart for controlling the average diameter and find its lower control limit.