$Ina{\displaystyle \underset{i=1}{\overset{25}{}}}{\stackrel{}{x}}_i=195,{\displaystyle \underset{i=1}{\overset{25}{}}}{R}_i=10$

The specifications for the $pH$ value are $7\mathrm{.}5+-0\mathrm{.}5.$

$a.$ Find the $\stackrel{}{x}-$ and $R-$chart control $limits.$

$b.$ Find the $1and2\stackrel{}{x}-$chart $limits.$

$c.$ What fraction $of$ the output $is$ nonconforming

$(assuming$ a normal distribution $ofpH$ values$)?$