A services process $is$ monitored using $x^{-}$and $R$ charts. Eight samples $ofn=10$ observations have

been gathered with the following results:

$a.$ Using the data $in$ the table, compute the center line, the upper control $limit,$ and the lower

control

$limit$ for the $x^{-}2\mathrm{.}5,5\mathrm{.}5,4\mathrm{.}6,3\mathrm{.}2,4\mathrm{.}6,3\mathrm{.}2,4\mathrm{.}0,4\mathrm{.}0,3\mathrm{.}6,4\mathrm{.}2$