$[10$ points$]$ Three ice$-$cream packing machines at the Creamy Treat Company are being evaluated for

their capability. If design specification of the ice$-$cream packing process is $16\mathrm{.}00\backslash$pm $0\mathrm{.}20$ ounces. The

following data is recorded.

a$)$ Compute the process capability indexes Cp$,$ Cpl$,$ Cpu, and Cpk for each machine.

b$)$ Which machines are capable of achieving four$-$sigma performance $($the four$-$sigma

performance target value is $1\mathrm{.}33)?$