Thirty-two samples of 8 items each were collected from a process. The average sample mean is 12 and the average range is 0.10. The upper and lower control limits, respectively, for an:
X bar Chart are:
a. 12.04 and 11.96.
b. 12.07 and 11.93.
c. 12.10 and 11.90.
d. 12.30 and 11.70.