The UCL and LCL values from $32$ boards with an average of four knotholes $($defects$)$ per $6-$foot board are:

$18$ and $0$

$10$ and $0$

$13\mathrm{.}4$ and $0$

$10$ and $-2$

$13\mathrm{.}4$ and $-1\mathrm{.}35$