A manager wants to build control limits for a process. The average values of the sample means and range for the process are $10$ units and $2$ units respectively. If samples of size $9$ are to be taken, the UCL and LCL for $x-$bar chart will be:

A$.-8$ and $28$

B$.10\mathrm{.}7$ and $9\mathrm{.}3$

C$.12$ and $8$

D$.4$ and $16$

E$.8$ and $12$