Thirty$-$five samples with sample size $5$ have been collected from a process which is grinding the outside diameter or journal bearings are $4\mathrm{.}5+/-0\mathrm{.}050$ micro$-$inches. Sum of X$-$bars and ranges based on the samples collected are $157\mathrm{.}85175$ and $2\mathrm{.}18750$ micro$-$inches, respectively. Assuming the process is running under a constant system of common causes and follow a normal distribution, What is the cpk value of the above process?