$(12$ pts$.)($a$)$ Consider a perfectly$-$centered process operating at a $2-$sigma quality level $($follows

standard normal distribution$).$ What is the defect rate, in ppm$?(6$ pts$)$

$($b$)$ For the $2-$sigma level process, suppose there is a $1\mathrm{.}0-$sigma shift in the process mean. What is the

defect rate, in ppm$?(6$ pts$)$