Calculate the control limits for an x chart, based on the range.

A quality engineer in charge of a coffee filter pack production line was concerned about the weight (in grams) of the filter packs being produced. The quality team sampled three packs every hour, throughout the production day. The table below shows the results: Sample number 1 2 3 4 5 6 7 20.6 20.1 20.6 21.5 21.4 21.1 21.4 Weight (g) 21.1 20.0 21.2 22.2 21.1 22.3 20.9 20.7 20.3 21.3 21.4 19.9 19.9 21.1