A process with a $1\mathrm{.}5$ sigma shift in its mean has a process performance index of $1\mathrm{.}2.$ Find the process capability index.

a$)5\mathrm{.}1$

b$)0\mathrm{.}7$

c$)1\mathrm{.}2$

d$)3\mathrm{.}6$

e$)$ none of the above