57) Random samples of four items are selected from a manufacturing process at regular intervals and a certain quality characteristic is measured. After 25 samples, EX = 15,350 and ER = 411.4. To construct a mean chart, what is the value for R-bar used to compute the limits? A) 411.4 B) 614 C) 16.46 D) 102.88 58) Random samples of four items are selected from a manufacturing process at regular intervals and a certain quality characteristic is measured. After 25 samples, EX = 15,350 and ER = 411.4. What is the sample size? A) 4 B) 25 C) 100 D) 20