10. Calculate the sides of the parallelogram

The points $A(20, 9)$, $B(-15, -3)$, $C(-15,-18)$ and $D(20,-6)$ in order are the vertices of a Parallelogram. In the parallelogram the opposite sides are equal. Calculate the side values of the parallelogram using distance formula.

 

$AB =$ $\sqrt{i}$.