Question $6(25$ points$)$

What is the UCL for the R chart?

Question $6$ options:

$2\mathrm{.}30$

$8\mathrm{.}92$

$7\mathrm{.}05$

$7\mathrm{.}27$

$8\mathrm{.}61$

$1\mathrm{.}80$

$2\mathrm{.}70$