1968 AMC 12 Question 6 - thichhoctoan.com

Question 6

Let side $AD$ of convex quadrilateral $ABCD$ be extended through $D,$ and let side $BC$ be extended through $C,$ to meet in point $E.$ Let $S$ represent the degree-sum of angles $CDE$ and $DCE,$ and let $S'$ represent the degree-sum of angles $BAD$ and $ABC.$ If $r=\frac{S}{S'},$ then:

$r=1$ sometimes, $r\gt1$ sometimes
$r=1$ sometimes, $r\lt1$ sometimes
$0\lt r\lt1$
$r\gt1$
$r=1$