Intriangle$ABC,$lettheanglebisectorsbe$¯BY$and$¯CZ$.Given$AB=8$,$AY=6$,and$CY=3$,find$BC$.[asy]pairA,B,C,X,Y,Z,I;A=(0,0);B=(1,0);C=(0.8,0.7);X=intersectionpoint(B−−C,A−−(bisectorpoint(B,A,C)));Y=intersectionpoint(A−−C,B−−scale(6)∗((bisectorpoint(C,B,A))−B));I=intersectionpoint(A−−X,B−−Y);Z=extension(A,B,C,I);draw(A−−B−−C−−cycle);draw(B−−Y);draw(C−−Z);label("$A$",A,SW);label("$B$",B,SE);label("$C$",C,N);label("$I$",I,SW);label("$Y$",Y,NW);label("$Z$",Z,S);[/asy]