Sarah Soliz, Director of Quality Programs, Is Designing $\bar { x }$

Sarah Soliz, Director of Quality Programs, is designing $\bar { x }$ and R charts for the rod shearing process at Stockton Steel.She has 26 samples of rod length, and each sample included measurements of 5 rods.The mean of the 26 sample means is 112 inches, and mean of the 26 ranges is 0.15 inch.The centerline for her R chart is ____.

A) 0.15
B) 26
C) 5
D) 112
E) 15