Six samples of five observations each have been taken for a process. The sample means and ranges computed $($in minutes$)$ are, $($mean$,$ range$)$: $(3\mathrm{.}81,0\mathrm{.}75),(4\mathrm{.}03,0\mathrm{.}43),(3\mathrm{.}94,0\mathrm{.}66),(3\mathrm{.}71,0\mathrm{.}46),(3\mathrm{.}68,0\mathrm{.}58),$ and $(3\mathrm{.}95,0\mathrm{.}78).$ Compute the upper control limit