\([asy] size(6cm); pair A,B,C,D,O; A=(0,9); D=(12,0); B=(5,5); C=(5,1); draw(A--O^^O--D,dashed); draw(A..(A+B)/2+(0,-1)..B--C); draw(rightanglemark(D,O,A,20)); dot(Label("A",A,N)); dot(Label("B",B,N)); dot(Label("C",C,W)); dot(Label("D",D,E)); dot(Label("O",O,S)); label("9 feet",A--O,W); label("12 feet", D--O,S); label("4 feet",B--C,E) ; [/asy]\)doesn't work