19. In $\triangle A B C$, $\angle C=90^{\circ}, A C=3$, $B C=4$. In $\triangle A B D$, $\angle A=90^{\circ}, A D=12$. Points $C$ and $D$ are on opposite sides of $A B$. A line through $D$ parallel to $A C$ intersects the extension of $C B$ at $E$. If $\frac{D E}{D B}=\frac{m}{n}$, where $m, n$ are coprime positive integers, then $m+n=$ ( ).
(A) 25. (B) 128.
(C) 153.
(D) 243 .
(E) 256 .
$\mathrm{B}$