A manager wishes to build a control chart for a process. A total of five (05) samples are collected with five (05) observations within each sample. The sample means (X-bar) are; 15.36, 14.61,16.36,20.28, and 15.77 respectively. Also, the corresponding ranges are; 10.79, 8.37, 2.81,8.17, and 3.31 respectively. The lower and upper control limits of the x-bar chart are respectively ot Select one: O a. 18.55, 13.47 b. 12.40, 19.72 c. None is correct d. 12.60, 20.36 e. 16.55, 11.47