The upper and lower specification limits on a valve diameter are $11\mathrm{.}01mm$ and $10\mathrm{.}98mm,$ respectively. Measurements in $60$ valves resulted in a mean of $10\mathrm{.}991mm$ and a sample standard deviation, $,$ of $0\mathrm{.}0035mm.$ Given the tolerance and process limits$,$ what is the capability index, $C_p,$ of the process?

A$.0\mathrm{.}90$

B$.1\mathrm{.}4$

C$.1\mathrm{.}8$

D$.2\mathrm{.}9$