A concrete lined triangular channel, with a Manning's $n$ value of $0\mathrm{.}013,$ a bed slope of $0\mathrm{.}28\%,$ side slopes, $s=1,$ and a depth of flow of $9$ feet is to be evaluated. Select the hydraulic radius $R_h$ from the choices below.

$0\mathrm{.}98$ ft $.$

$1\mathrm{.}94$ ft$.$

$2\mathrm{.}68$ ft $.$

$3\mathrm{.}18$ ft $.$