Question 25
Let $ABCD$ be a parallelogram and let $\overrightarrow{AA'},$ $\overrightarrow{BB'},$ $\overrightarrow{CC'},$ and $\overrightarrow{DD'}$ be parallel rays in space on the same side of the plane determined by $ABCD.$ If $AA'=10,$ $BB'=8,$ $CC'=18,$ $DD'=22,$ and $M$ and $N$ are the midpoints of $A'C'$ and $B'D',$ respectively, then $MN=$