=+Subgroup x1 x2 x3 x4 13 13.00 12.96 12.99 12.90 14 12.88 12.94 13.05 13.00 15 12.96 12.96 13.04 12.98 16 12.99 12.94 13.00 13.05 17 13.05 13.02 12.88 12.96 18 13.08 13.06 13.10 13.05 19 13.02 13.05 13.04 12.97 20 12.96 12.90 12.97 13.05 21 12.98 12.99 12.96 13.00 22 12.97 13.02 12.96 12.99 23 13.04 13.00 12.98 13.10 24 13.02 12.90 13.05 12.97 25 12.93 12.88 12.91 12.90

a. Construct an R chart for this data. Are there any out-of-control signals present?