C$-$Spec, Inc., uses an automatic machine to mill an engine part. Four samples

have been taken to monitor the length $($inch$)$ of output. In each sample, there are

five observations

Determine the three$-$sigma upper and lower control limits for the

$$mean chart using sigma$.$ Assume that the standard deviation sigma of the process is

$0\mathrm{.}1.$ Is the process in control? If not, explain why.