$6.($a$)$ Suppose that a process is currently operating at a $3\mathrm{.}5-$sigma level of quality, and it is planned to use improvement projects to move this process to a $6-$sigma level? What project improvement rate would be necessary to achieve that new performance in $2$ years? $($b$)$ Suppose that your business is operating at the $4\mathrm{.}5-$Sigma quality level. If projects have an average improvement rate of $\backslash (50\backslash \%\backslash )$ annually, how many years will it take to achieve Six Sigma quality?