$3\mathrm{.}1$ Determine $L_p,L_r,M_p$ and $M_r$ for the following shapes. Use table $3-2.$

$($a$)$ W$12$x$16$

$L_p=$

$L_r=$

$M_p=$

$M_r=$

$($b$)$ W$18$x$35$

$L_p=$

$L_r=$

$M_p=$

$M_r=$