specifications for a particular quality characteristics are $\mathrm{.}65+/-\mathrm{.}01$ in$.$ Thirsty $30$ subgroups of size n$-9$ are sampled from the process. Trial charts are established, and the process is found to be in statistical control. From control chart x double bar $=\mathrm{.}651$ and R bar$=\mathrm{.}009$ estimate the process standard deviation